Entrapment is a possibility- tread carefully.
I like Nicole's idea best- "hey, can I borrow your torque wrench? You know, the one under the purple teddy" or whatever it was. If he was concerned about security, he would've locked it or found another place to keep it. If his reply is positive, or denying (indicating entrapment is not the purpose), then you could say "I've got a toolbox like that, too" or something to that effect.
My first reaction is that he is a CDer, and suspects you are, too (no lock on the toolbox, etc), or at least wouldn't be surprised if you are.
Of course, if he's only a novice at sneaking, he may have thought his stash secure. Wait, and watch- a moment will present itself eventually.
