So Megs, has this show occurred? You can still go try and get a ticket outside the venue.
The worst is: "It's not you it's me." No, wait, sorry, I meant, "Sorry, I no longer can sell you the tickets. I forgot a friend of mine put these tickets on eBay and they sold." :p
What can you do? I've been there and it's frustrating. Tough to change someone w/ no etiquette.
Be provactive and find another person or method to get your tickets.