Someone has been eating my food that I SPECIFICALLY labeled as MINE for 2 weeks now and I'm tired of looking at a half eaten sandwich everyday!
-sighs-
I think that crying over this situation is kinda baby-ish. However, if you're tired of seeing your food being eaten, go across the street during your break and buy a sandwich or whatever you want.
Or, make lunch that doesn't need to be refrigerated so that person won't have to sneak in and take a bite anymore