How do you spot a thief in a classroom?

Odds are most of us have experienced it before, and this is not the first time it's happened to me. It's the first time for this particular class, however.

Someone has taken 2 self-inking stamps (they say 'good job', 'thumbs up,' etc.) It's really bugging me because they were a bit sentimental to me. My old team gifted them to me when I changed districts.

I really want to address this particular theft in a big way. I want to address it Monday morning at my morning meeting. Is that wrong? Should I not make a big deal out of it? I mean, I'm hurt and I want them returned, but I don't want to say the wrong thing or whatnot.

I'm curious how others have handled a similar situation.

By there actions and eyes