Serious suggestion: Paint some of your stuff with UV reactive stuff and shine your roomies. Might be expensive though. Hmm, maybe something to do with odour. Smear something citrusy on your stuff and.. eh, go smell your roomies. Oh, oh! Parfume! That'll work. Spray your peanut butter jar with parfume (wich doesn't smell as much when cold) and you'll eventually get your crook, I think.