I had something similar going on, but it wasn't so secret. Thinking I was being very clever, I mounted a bottle opener above the garbage can in the kitchen. Except our garbage can has a lid (one of the spinning types), so everytime I opened a bottle, it normally bounced off and either landed on the floor, or went behind the stove. I'm sure I've got at least 100 caps back there. My wife saw me a few times and complained, but didn't really bitch about it.
I then got more creative and hung a hard drive magnet below the opener. Works like a charm and holds about 11 caps before new ones start bouncing off.
My next step is to embed this into the wall and paint over it. I'll have to do that when the wife is away, she has already vetoed that idea.
Enjoy
KingMonkey