I can't see the fraud. 

Your buyer exercised their right to use the money back guarantee. 

You refused to accept the return.

Ebay did what they always do in this situation, refunded with your money and told the buyer to keep the item.

Had you accepted the return and received something back other than  the card you sent, then there would be grounds for fraud and we would have suggested a report to Report Fraud,  as AF is now called.