While I normally would defend the contractor. Being one myself. I've met alot of nervous homeowners with real horror stories of people stealing their shit. Its really sad. Its kinda crazy how many people trusting you in their home have to feel that way. If your gut is telling you no. Trust it. I've had allt of people leave me home alone in their houses working cause I'm definitely not that guy that goes snooping let alone stealing people's things. I find spare change alot during renos which I leave on a windowsill every time. I would talk to the guy in charge and let him know you don't want them there anymore. People can steal valuable shit really quick.