if you don't have time to re-auction it and the person doesn't
come through, offer it to the second highest bidder.  It's happened
to me before, and I was pretty excited to hear from the seller.

although, with it just being a day, it's *way* too early to even
think about it.  I always specifically request a response/address
and I still have a lot of bidders that don't email me back at all--
I just get their letter about a week later.

rosemary