If you call up the credit provider, they will be able to look up a listing called “Merchant Code” against what has been recorded against the transaction. It will tell you what type of business that the transaction was for. If he purchased it online, there is also a chance that an invoice was sent to his email address, so I guess that you could try getting him to show you his email, and cruise around in the inbox, trash and any folders for it. Or on ebay if purchased there. Good luck