I've had three instances happen during my trips:
-- Lost a light from the bike in Fort McPherson, NWT, Canada when cycling the Dempster Highway
-- Lost a bicycle bell when the bike was locked up underneath a hotel in Mysore, India
-- My riding partner had some hoodlums steal her bicycle pump in small village of Ушумун in Russian Far East.
I carry a lightweight lock and chain, though there have been entire trips where I didn't lock it up. I started being more diligent on locking after loosing my commuting bike at home outside a local grocery store. What I have done on more remote trips is carry some spare essentials like bike pump and also make sure I'm carrying things like passports and $ on my person.