Question about Auction sites when props come back on market

[Shari Posey]

When a property comes back on the market on hubzu.com, does that mean the buyer backed out or has something fishy occurred? I have my eye on one property that had met the reserve at the end of the auction but is back on the market less than a week later with the same list price. When the auction was over last week, the high bid plus the 5% premium was way too much to pay for the house so I'm wondering if the site has fake bidders or something. If the winning the buyer didn't sign the contract you would think they would go to the next highest bidder rather than start all over with low bidders.