We were told by an employee of the theater that the rush tickets could be exchanged for another rush. Essentially, they are $30 tickets that can be exchanged for $30 tickets. So, if we (and by 'we', I mean my daughters) go early another day, we can get tickets for another performance.
"It does me no injury for my neighbour to say there are 20 gods or no god. It neither picks my pocket, nor breaks my leg."
-- Thomas Jefferson