IMHO you're in the clear. You were acting as an agent of the seller and you received a good offer for the strike. You did what any good agent would do and relayed the offer to the seller. It was the seller's decision to end the auction, and you did what he wished. IF anything, you shorted yourself on the commission (or so people say afterwards--always easy to do), but the seller opted to not take the chance that someone would bid $2500, have no one else bid, and end up selling for 99 cents.