My money is he had a puncture, locked the rest of the bike up and took the wheel to fix the puncture when he had more time... But obviously the idea he had his bike stolen is very amusing.
I guess him recovering the helmet and wheel is a possibility, not something I'd thought of. The guy looked pretty forelorn though. Don't think the puncture theory makes much sense.
My money says he had his bike nicked, but if that's the case then where's the lock?