Member listings do not exist any more. GoDaddy sometimes run events during which non-expired domains are auctioned but they require pre-approval and do not include the option to Buy It Now. A domain being recovered
after winning it at auction is typical (due to redemption) but that isn't what happened in this case given GoDaddy acknowledge some sort of "issue".
The transaction assurance team typically handle Afternic transactions. My best guess is that you weren't seeing an auction domain but an Afternic domain. Afternic
usually removes domains automatically when their ownership changes but it is possible that the process failed for some reason, and the domain remained listed despite having changed ownership. If fast transfer was enabled, then it is quite possible the domain was sold to you without knowledge of the owner.
Are you sure that this happened via GoDaddy Auctions, and not Afternic? Can you share the order confirmation? Nothing can be done to get the domain back, but it will be interesting to know what happened