A second BINGO!
If you are going to be gone momentarily, it may behoove you to leave the engine running instead of running the starter again.
If you roll down a window, you don’t need to worry if the door is going to lock when you close it.
To recap:
Engage lock from the outside, using the key.
Never close all doors on a running vehicle without an open window or other easy-access opening.
p.s. - a key in your wallet is going to wear a hole in it.
I’ve been using a key holder for my wallet for over 20 years.
To help keep myself from locking the key in the trunk, I’ve made a habit of leaving the key in the lock while I load or unload. I never take the key out of the lock while the trunk is open.
I was in the habit of stopping car, removing key from ignition, opening door, etc. all in one unconscious operation. So, when I stopped the car to contemplate my errand before opening the door my pattern was broken, and car keys ended up locked inside. (The errand and its need for contemplation spice up the incident but this is the abridged version. 
)
A locksmith came when I called, and impressed me; I drove a little and parked, contemplating my errand again along with possible ominous meaning of the key locked-in-car. Again the pattern was broken and again … You guessed it!
These days I’m so absent-minded I try to be very careful. Approaching a trash bin yesterday with car keys and trash item in hand, I made a point of putting keys in pocket before nearing the bin.
Yes. I’ve never locked my keys in car, except the one day 38 years ago when it happened twice.
When I was learning to drive, my father encouraged me to develop the habit of always locking the driver’s door with the key, as then I could be sure I wasn’t locking the key in the car.
I believe he suggested that locking the door by pressing the button down on the door before you closed it was lazy, and of course it runs the risk of locking the keys in the car. So my suggestion would be to train yourself to do that.
I don’t know if Volkswagen has changed this, but back when their cars were air-cooled you needed to lock the driver’s door with the key, as the mechanism was designed to unlock the door when you closed it.
This isn’t 100% foolproof. On one of those air-cooled VWs, I was intentionally leaving the car running when I got out, but when I closed the door the lock button slid down just enough to engage the lock, and VWs are notoriously hard to open with a slim-jim. Some nice police officers did manage to get my door open for me, but it took a while.
My other advice would be basically a form of what you’ve been doing: have a plan for what to do if you lock your keys in the car. Have a spare set and keep them somewhere specific at home, or give them to a friend, or both. Then if you do lock your keys in, it is a small inconvenience as you take a bus home to get the keys, or call your friend to come help you. (This assumes the bus is an option where you live, but the specifics of the plan can be changed for your situation.)
As far as I’ve ever known, this was a universal feature in all car door locks, at least before the advent of electric door locks. Of course, I only ever owned a VW and various Japanese cars. (Well, and an Oldsmobile, but that was so long ago I don’t remember how it worked.) Did American-made cars not work this way also?
My strategy, discussed earlier, of training myself to ALWAYS use the key to lock the door, was most specifically aimed at forcing myself into the habit of NOT locking the door by just pulling on the outside handle when closing the door.
So you’re okay if you lock yourself inside the car…but…
One guy I know said someone told him to hide his spare key under the license plate, held there by the screw that fastens the plate to the car. As with other hiding places, that’s too many people who know the trick for my taste. I agree with all the carry two keys and lock the door with the key people.
As far as old cars not locking when you shut the doors, the first car we had that would let you shut a locked door was a '62 Chevy, and you had to hold the outer handle button in when you shut the door. I had a '63 Studebaker - it was impossible to get the front doors to lock without the key, but the back doors would shut locked just fine!
Back years ago when we went out of town to the big city of Duluth Christmas shopping and not being used to locking the car doors (more like usually even leaving the keys in the ignition) anyway as i walked away i notice i had left the headlights on. I then found out i did not have the door key as that make (some Chrysler product) the door key was the same as the trunk, so i took out the leatherman tool and removed the headlamps to keep from draining the battery. I then called the local police only to find out they do not open cars and i had to call a lock smith, well holiday weekend and all, being a Fireman i walked to a nearby fire station to borrow a slim Jim (we called a window jimmy) and they did not have one and said they had never seen one! So i see a workshop and ask if they have any sheet metal and they do so i cut one out of galvanized sheet metal. It worked just fine and for the rest of that afternoon we would lock the doors and i kept the jimmy in the fuel fill cubby.
Just a few years ago while deer hunting the neighbors came over to my hunting shack with their dilemma, they had locked their SUV out in the woods with keys inside and didn’t know what to do. I cut another Jimmy out of a stove pipe and used it to open their vehicle, only problem was the alarm system went off and we are out amongst all the other hunters, but it took less than 2 min to get in and silence the alarm.
We used to practice with the window jimmy, but now days the firefighters just pop the windows with the cool little punches they all carry.
I learned my lesson when I locked my keys in the car once. It was starting to rain, and I needed to put the top up! :eek:
My very first wallet had a space in it for spare keys, one marked “car” and one marked “house”, which together were the size of one of the credit card slots. My father told me never to use those. I asked why, and he said “because then anyone who takes (or finds) your wallet also has keys to your house and your car. Your ID has your address on it, so he knows where you live.”
I have never seen this, but I have seen its exact opposite: a car with electric locks that automatically locked the doors when the engine started. While I can see the appeal, I think that “feature” would drive me batty if I actually owned that car.
