<human>: Can you succinctly summarize the text in 1-3 sentences?

Basically, someone is stealing our food.  There's 4 of us living in the apartment, and the only suspect there is our 4th roommate that we barely ever see.  But he seems like a really nice easy going guy so we don't suspect him.  That leaves our friends who are coming in and out of our apartment.  It's kinda a Seinfeld scenario where people will just come busting in.  And occasionally we will forget to lock the door when we leave, and by occasionally I mean pretty often, and this is probably when they steal our food.  We already caught one friend taking seasonings and stuff without asking so he's our primary suspect.

Anyway, any suggestions on how to catch the guy?  Locking the door is the main solution of course, but we kinda wanna know who did it so we can have closure.  So any booby trap ideas, or cheap spy equipment suggestions would be awesome.
<bot>: Someone is stealing our food and we want to catch him.  Suggestions on booby traps or cheap spy equipment?