That's a tough one to call.
I'd go with your instincts, if you've had no problems in 2 years why would he steal now ? People mislay stuff all the time and look to blame anyone but them for mislaying it. It might just turn up somewhere.
I know this seems OTT, but what about a honey trap or two for him, arrange to do a house, even a friends house or something and leave a few temptations about, that will tell you for sure I'd have thought. Or is that out of order to do that I don't know.