Mistakes dó happen yes, but... it is a bit foolish to lose an item you listed to sell
I myself am always a bit suspicious at these things. Once i won a lot of ponies for a really nice price and the seller made up a story about shipping costs being around $100 (believe me, in NO WAY that was possible) and some other excuses. I am not saying that it will go the same for you, but i think there are sellers who make up stories when they did not get the amount of money they'd expected.
The seller in my experience just replaced the lot i originally won and got twice as much this time.
It was so unfair i cried about it.
But i think its best to wait maybe a few days and keep a real good eye at ebay, or just they person's listings.
I hope you'll get your pony though!