Pull out your phone and say "You don't mind if I get a picture, just in case...". If he doesn't care, it's his (if I was in that position, I'd gladly pose for the picture). If he threatens to take your phone and insert it somewhere, you announce in a loud voice "Hey everyone, this guy's stealing a board! Have a good look!".
Depending on the day. If my board lock just screwed up and im resorting to unscrewing my bindings to get my board off i'm prob gonna be far from a good mood. If some jerkoff then walked up to me and asked for a picture i'd probably say, No. If im going through all that. If he then announced "hey look, he's stealing this board" I'd be pissed off and ready to fight. Prob tell you to go get security and mind your own fucking buisness.
*For some reason I picture a hipster asking to take the picture, so that might of had a help in my emotion in this post.*
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