Never had anything stolen and like you I don't like being left alone with their belongings so I go into the kitchen and clatter about until they come out. I also always ask them as they are heading out.."Now do you have your wallet, watch, phone, keys and specs?" I also check they have their flies zipped up as some forget...lol.
Lol. I check their zip and occasionally hair/tie, I feel like a mother sending a son to school. There you go darling now you look decent so off you go!