I would contact GD after 7 days and tell them to tell the buyer to sh*t or get off the pot.
I've sold a dozen or so domains via GD auctions and they usually do take a while for transfers and stuff.
Also, be prepared for aggravation if the domain isn't registered through GD. I moved a number of domains from GD to Namecheap and as they sell, when I try to transfer them back, I get errors and GoDaddy support is useless.