This is of course after the fact, but when we moved into our old-ish house when we got married, one of the first things I did was find which circuit controlled which outlets and lights. Took a couple of hours using my circuit tester and running up and down the stairs, but I finally got everything mapped out. I typed everything up, printed it out and hung the paper by the breaker box. Time well spent.
Same deal - the downstairs bathroom is under the upstairs one- so the GFI downstairs also controls the upstairs bathroom.
IANAelectrician, but this is my understanding -
GFI only trips itself and any outlets downstream to off, so it should be the first outlet on the circuit that needs protection - although if other outlets are before it and not near water (i.e. not bathroom, kitchen, outdoor, etc.) then those can be upstream. If the GFI is in the bedroom before the bathroom, then either it’s a very cautious electrician - or a lazy one.
The outlets upstream (between GFI and circuit breaker box) do not have the GFI protection - they will not lose power if there is a fault detected.
However, if it’s a GFI circuit breaker, the whole circuit is protected.
Some literature says multiple GFI outlets on the same circuit are ok, others say they make the circuit unstable and more prone to trip. At the least, two on the same circuit is a waste of money.
(My understanding is that code usually says “no more than 5 devices - lights, outlets - on a circuit.” Lazy electricians, or cost conscious, will wire as much as they can in one area. In my house it seems they ran specific runs for just the kitchen and also just the bathrooms. The outdoor outlets are at the end of the runs. )
I did this using a radio - volume turned way up - and standing at the circuit box.
I did about the same, but I used a circuit tracer.
Found some interesting garbage. 1 circuit has all the outlets and lights of 3 bedrooms, plus 1/2 the master bedroom, and 3 outside outlets, and one set of kitchen lights on one circuit. That is a total of 20 outlets, 3 sets of lights. If a vacuum cleaner is plugged into that circuit the lights go dim and the voltage at the outlets will drop to around 109 volts. Then I have another circuit with the stove, microwave oven outlet, Pantry lights, and a 3/4 Hp fountain pump all on the same 20 amp circuit. We cannot run the pump and cook dinner at the same time, the circuit will have 23 amp on it. Fun. I am slowly re wiring.
Does it matter where in the “stream” the GFCI is located?
I’ve been meaning to do this for 25 years. What are you doing this weekend? 
mmm
I am not an electrician, but I’m pretty sure that it only protects outlets that are connected to its load terminals. It should be the first thing on the “hot” side of the circuit.
I am also not an electrician, but based on personal experience, this is correct.
In-laws invaded my house last night. I am available any time. Please call.
But wait…don’t you have to run upstairs every time anyway to move the radio to another outlet?
mmm
The apartment in which @Seanette and I live has a GFCI receptacle in the back bathroom. The receptacle in the front bathroom, and an outside receptacle on our patio, are daisy-chained off of that same GFCI in the back bathroom.
And just to correct a very commonly-misused bit of terminology. What nearly everyone calls an “outlet” is a receptacle. An outlet is anywhere that electrical power is taken from a branch circuit, to be used. A receptacle counts as an outlet, but so do things like lighting, HVAC, ceiling fans, ventilation fans, and anything else that gets its power from the house wiring, even if it is not connected via a plug/receptacle—all of those are outlets.
Just wondering, @Bob_Blaylock, are all professional electricians this pedantic, dear?
Not really. It seems to be a reputation I have developed among my fellow electricians.
But as long as you’ve known me, you should know well that I’ve been this way since long before I ever knew what twists my career would take, to lead me into this profession.
My dad’s also an electrician. He’s also pedantic. Draw your own conclusions. 
That, to me, is quite shocking. I thought most electricians were well-grounded.
Once you find the breaker that shuts off the music, then you can try all the outlets in the same general area (and the lights, fan, et. if you mean “outlet” as receptacle. Generally the circuit daisy-chains from one outlet/device to another. I’ve found a few where the circuit splits, i.e. wiring in and 2 wirings out. Done by a real electrician, so the extra wires joined by barrettes behind the receptacle.
Again, circuit is a daisy chain (with possible branches). Circuit goes in one side and out the other. Only the GFI itself and anything further along will experience a power outage when the GFI trips. So if that circuit goes to the kitchen, say, then the first receptacle at which the wires reach the kitchen should have the GFI - since the outlets closer to the circuit breaker would not be protected.
This as I understand is the reason for the “5 outlets” code. Back in the day, a typical lamp would be 60W to 100W. You can see that 5 lamps could overload a 15A circuit. (In a living room, it might not be unusual to have 3 lamps in the same area). Obviously, 2 devices like a kettle or toaster can’t run 1000W at the same time on one breaker (except maybe 20A), so a good modern well-wired house should have a decent number of separate circuits in the kitchen.
Yeah, ours is a receptacle next to the breaker box. Controls bathroom outlets, exterior outlets, and ONE light in ONE bathroom. When we used to do Christmas lights, the circuit would trip when it rained. I’d know because that light would stop working.
If the OP hasn’t found the GFCI outlet, look under the sink. IIRC electricians tend to GCFI that outlet if it exists and then run the leads downline from there. Admittedly that is more common in kitchens than bathrooms.
Code requires at least 2 circuits for the receptables in the kitchen. Plus the outlet for the dishwasher and garbage disposal should be on a separate circuit. Same with the range and range hood. At one time refrigerators were expected to be on a decanted circuit, but now inspectors are laxed on that one. New modern refrigerators are no longer high amp appliances.
Still haven’t found it. I swear I’ve seen it in the past but can’t possibly find it now .
It’s not
- Under sink
- In any bathroom
- Garage outlet closest to breaker box
- Garage outlet next to interior door
I’ve been looking at every single outlet since then and no dice.
Maybe it is not a GFCI issue. You know how light bulbs may blow after a power outage when the power comes back or you hit the switch? I believe that’s due to the lack of any inductance just as the current starts to flow flows. It would be bizarre and I’ve never heard of it happening but what if when the power came back it in effect “blew” the circuit meaning it broke a wire somewhere upstream or rather melted a section of it at the connection to the box. Is such a thing even possible with the gauge of wiring used in home wiring? If so and it was in the box, is that why a fire didn’t start?
Just spitballing here.
Have you checked to see if the breaker itself may be faulty? Just because it “clicks” it may have other issues. A 40 year old house the wiring panel should be pretty well labeled, if you are somewhat mechanically inclined take the front cover off (the breakers stay in place) and visibly check the whole circuit breaker for the circuit that isn’t working. I have basic knowledge of household electricity and will change out an outlet or fixture but when it come to working IN the breaker box I call a professional.