If your story is accurate, the cards are stolen, aka hot. It's illegal to knowingly sell items you know are stolen, even if you bought them innocently. The cards would have to be returned to you, and the second buyer would be entitled to a refund from the seller he bought the card from. If the second person has been informed the card is stolen, he should be aware that he himself would be breaking the law by reselling it.
I just wrote an article on this very subject:
The Importance of Provenance in Collecting