How do I identify the Apple Pay card used for an online purchase and return?

I've looked at my transaction history for all the cards associated with Apple Pay and none show the transaction of the purchase. I know I used Apple Pay, since I have a receipt that states as such. The issue is that I returned the product I purchased 2 weeks ago and still haven't seen the money. The vendor says there is nothing more they can do since they've processed the return and it went back to the ApplePay card that was used. I don't see the purchase OR the refund on the cards associated with my ApplePay. If I knew for sure which one I used, I could get ahold of that financial institution and deal with them directly, but until then, ARGGHH!! 

[Re-Titled by Moderator]