When I first moved into my previous university housing, I got a security camera for my bedroom. And I didn’t tell my roommates until months later when I knew I could trust them. I would suggest going down this route because it helps with other things too. Like it also helped when my university housing services decided to try to go into my room without notifying me (which they weren’t allowed to do due to me having an ESA).
Just throwing this out there but I would at least consider pressing charges on whoever it is. If you just want your stuff back and don’t want the hassle that’s fine, but if they’re bold enough to steal electronics like an Apple Watch I’m concerned you’re not the only one they’re stealing from.