The seller is responsible for getting the right coins to the correct bidders. It can be a pain in the rear getting the seller to contact the other winner, if they're the "once it's in the mail it's NOT my responsibility" kind of seller. This happened to me before, a couple of years before buyer protection, and it was weeks before the situation was corrected. Not only did I have to wait for the item, I was out the postage fee for shipping back the wrong item, which the seller should have repaid as the right thing to do, but didn't. It was a really annoying situation and I eventually reported the seller. Nowadays, you can just merely open a claim with PayPal and have them do all of the work. Good luck with getting a resolution.