Lets help them out by coming up with ways.
1) poisoned by bad tin of Cram, wake up in hospital room
2) fall into pit trap, have to leave behind equipment to climb frayed rope out
3) robbed while asleep
4) robbed while awake
5) powerful magnets
6) amnesia
7) underpants gnomes took it all
8) the old switcheroo- gas vents come on, character falls asleep, wakes up with ALL THEIR GEAR.