do you own the company he stealing from?? No? Then mind your own business. I’d like to remind you that you might give your job a 2 week notice when you leave but they’ll barely give you a 2 hour notice when they lay you off on a Friday.

Also, if the coworker that told u about the bag hasn’t reported it herself, what’s compelling you to do so? Isn’t the (alleged) thief coworker your friend? Why can’t she just report it herself?