I don't know if this is feasible for 9:30, but at other shows I've been to, like when I went down to Richmond to see Bruce Springsteen, you had to go pick up the tickets (this just applied for floor seats I think,) in person, with ID, credit card, confirmation # etc, they watch you put the wristband on and send you straight into the venue, with absolutely no chance for ticket turn around.
I didn't go to the Foo Fighters show, but didn't something happen like this? While it can end up sucking for people who can't go and can't resell their ticket, it does put a cap on the scalpers for hot ticket shows like this one.