They have no way of knowing what your auto bid was, they could have legit put up a bid of $53.50 and called it quits.  The only way for this to be a scam .... would be for them to bid you up, until they are in lead by $1, then have the seller remove the leading bid, which would have left you in front. You could contact Trade Me via the live chat, give them the Auction number, and they would be able to review the bidding activity.