When we process a refund, the bank doesn't let us know if the card has been cancelled, it's really between you and your card issuer. When we process a refund to a card that has been cancelled, the funds are held by the card issuer.
You'll need to contact your card issuer and let them know that you have received a refund to a card that has been cancelled, this should help them understand what happened.
You will need to give them the date, time and amount of the refund to help them locate your money, you can find this information in the refund confirmation email that we sent on the day we processed the refund. If you need help finding this information get in touch with us by submitting a request.