Either you misunderstood what someone said, or they were wrong.
Most appliances don’t contain enough current to RELIABLY kill you. Most contain enough current to POSSIBLY kill you.
Electricity typically tends to kill you in one of two ways.
At low current levels, electricity can screw up your heartbeat and throw your heart into fibrillation. Your heart has kind of a funny design in that the fibrillation state is stable. Get it into fibrillation and it will tend to stay in fibrillation unless something acts on it to take it out of fibrillation (like someone zaps your heart with a defibrillator).
It doesn’t take much current to throw your heart into fibrillation. Most safety standards are built around 5 mA (0.005 amps) being the “safe” level. Anything above that is dangerous. 6 mA obviously isn’t going to be too likely to screw up your heart, but as the current increases, so does the risk. Once you are up around 50 to 100 mA, you’re well up into the danger zone.
The thing is, this type of shock is very hit and miss. Your heart is significantly more likely to get thrown out of whack at certain times in its rhythm than others, so it’s very random. You might take a 50 mA shock across your heart and go into fibrillation and die. You might take a shock at double that current and your heart might not be bothered by it at all. It’s very random. But anything above 5 mA is dangerous, and 5 mA is a very tiny amount of current.
One funny thing that happens is that at first, the risk of death increases with the current. But then the risk decreases significantly. The reason for this is that at higher current levels, instead of the heart going into fibrillation, it is more likely for all of the heart muscles to just clamp. At that point, your heart isn’t pumping blood, so if no one removes the source of the current, you’re toast. But if the current is removed, the heart will generally start beating in a normal rhythm again.
If you continue to increase the current though, the fatality rate once again starts to climb. This is because you start getting into the second way that electricity kills you. It literally cooks you to death. Current flowing through anything that isn’t a superconductor generates heat. One demonstration that they used to do on science shows was they’d stick a nail in either end of a hot dog. Then they would attach each nail to one of the wires from an electrical cord, and plug in the other end of the cord into an outlet. Kids, don’t try this at home. We tend to call electrical cords with exposed wires on the ends “suicide cords”, for a good reason. But if you do this, you’ll cook the hot dog pretty darn quickly.
This is how the electric chair kills you. It literally cooks you to death. This is not so hit or miss. Very few people survive the electric chair, and those that do only do so because something in the chair failed to work properly. A perfectly functioning electric chair is 100 percent fatal.
Most household appliances don’t have enough current in them to reliably cook you to death, but most do have more than enough current to potentially screw up your heartbeat.
5 mA is barely a tingle. Your symptoms indicate a significantly higher shock level. You were well into the potentially fatal shock range.
One thing about electricity and the human body is that it’s not a simple linear resistor. A common (if oversimplified) model of the human body is often a resistor in series with both a resistor and a capacitor in parallel with each other. The thing is, the values of those components change based on the applied voltage. Low voltages, like 24 volts and below, won’t usually overcome the resistance of your skin, and it’s almost impossible to get any measurable current flowing. Once you get into the 50 volt range or so, then it starts getting dangerous. Anything that plugs into an outlet has a lot higher than 50 volts in it, and therefore can easily inject a potentially fatal amount of current into your body. At low voltages (below 24 volts), your body acts like a resistor with many megs of resistance. At higher voltages, like household AC voltage levels and above, that effective resistance value of your body drops down into the thousands of ohms range, and you get a significantly higher amount of current flowing.
Since people don’t tend to have CRT type televisions any more, a microwave oven is probably the most dangerous appliance in their house to tinker with. The high voltage output that powers the magnetron is typically somewhere between 1,000 and 3,000 volts, and it has more than enough current sourcing capability to totally whack out your heartbeat.
I wouldn’t say it’s a miracle that you are alive, because a lot of people have been shocked by microwave power supplies and haven’t been killed. It’s not anywhere near as reliable at killing someone as the electric chair is. On the other hand, while you think what you did was perfectly safe, you’re wrong. The chance of death was definitely not zero, not by a long shot.
If you are going to tinker with something, tinker with something that is battery powered. It’s awfully hard to kill yourself with anything operating below 12 volts.