Frozen car-door lock problem?

Kay soo... Tonight, I went to get into my car, and the key wouldn't turn all the way into the "unlock" position. I figured it was just a frozen lock, so I went inside and grabbed one of those small screwdrivers for eyegles, heated it up with a torch lighter, and pushed it into the keyhole. I heard a sizzling noise, figured it worked, and tried opening the lock again with my key. No luck. Eventually, I became impatient and started heating up the key itself and started trying to open the lock. STILL no luck. I went to the penger door, skipped the screwdriver part, and only used the key. I took the lighter to the lock itself and set it up there for a few seconds. Then, I light the key for a few seconds and turned it in the lock. It worked. I opened the driver door from the inside and went around and got in. I played around with the "lock and unlock" switch, and noticed that the thing wasn't going back and forth like it's supposed to (I drive a '91 Grand Marquis, if that helps anyone wondering what the "thing" is). I hit the lock on like 23456234 times, shut the door, and tried opening the door. It didn't open, but my key still wouldn't work in the lock. I handled that lock the exact same way I originally did to the lock on the penger side. STILL no luck. Did I go about de-icing my lock the wrong way? If so, how should I have done it? Is it possible that I caused mechanical damage to the lock? If so, is that an expensive fix? A homemade solution to a frozen lock with a high success rate would be terrific. Please and thank you.