I've watched other people's gear at OAR shows, never for an entire show, but at the Aragon this past tour, one guy was gone for about half an hour. It depends on how many other tapers are there watching their stuff, you can normally get away with it depending on who else is there. Also, get your stuff in some kind of bag so that people can't see what it is. If they see flashing lights, or if they notice it looks like an unattended CD player, it's as good as gone.
Have fun Connor!