Schrodinger's Keys

So my room is actually outside of my college's walls. It's a building called "the Warehouse," which is not quite as bad as it sounds, especially by MIT standards. However, I was given a huge set of five keys because of the various locks. I've figured out the numbers on a lot of them, but there are two keys that look almost exactly the same. One of these opens the outside two doors, the other opens the door to my hall.

The interesting point is the process of selecting these keys. I have determined that they are different, because one doesn't open the outside door, and the other doesn't open the inside door. I'm also fairly (although this is where it gets foggy) certain that both keys are useful. When selecting the keys, though, I always select the correct key to the outside entrance immediately. I then walk up a flight of stairs and subsequently select the wrong key.

I assume this is quantum mechanics at work at a macroscopic level, because whenever I concentrate my full attention on it, it almost makes sense (although sometimes not even then). Most of the time, though, I cannot figure it out.