How Did It Get To the 12th Floor?

I'm sitting quietly at my desk when all the sudden I hear a blood-curdling shriek. A girl I work with is standing in the lobby area of our floor shouting "roach, roach!"
Sure enough, there was a huge roach (at least 2 inches long) moseying along the tile floor. After a few minutes of laughter and a cell phone picture, I chased the roach into a conference room and caught it under a cup.
But when I tried to slid a paper under the cup, the roach ran away.
Fast little guy.
The elevators in my building are notoriously confusing. You select your floor outside the elevator and it tells you which elevator to take. When you get in, you don't press a button, you just wait to be lifted (or lowered) to your destination.

How did a cockroach figure that out?