[swarmee]

One of the auction houses has a rules sheet that includes language to the extent that: "We reserve the right to make bids up to the amount of the hidden reserve..." or some such. It's possible that this was occurring, and when no additional bids were made, they contacted the consignor and asked whether he/she would reduce the reserve to the current highest actual bid. When that happened, they killed all four bid increments, and you were left as the high bidder.

It's also possible that for some reason, you were outbid by an actual bidder, however he sent the auctionhouse a message saying that he intended to bid on a different lot or didn't realize he couldn't pay with Monopoly tender, and the auctionhouse retracted them. However, I would hope they would contact you and explain the situation. That's one reason I don't really like the blind bidding process many of these auctionhouses seem to have. At least with eBay you get a sliver of a screenname (6*****a) that you can see is an actual bidder, or whether you're bidding against one person or 30.