The issuing bank references the card numbers to account numbers. The issue is not an expired card.
Refunds, once approved and finalized by the merchant are forwarded to the merchant’s credit card processor. The processor debits the funds from the merchant’s bank account and sends them to the Payment Network Operator ( Mastercard, Visa etc.) and they forward them to your bank. Depending on weekends, holidays can take several days to a week or more. In my experience with refunds and banking procedures, the holdup is generally the merchant.
The merchant has to finalize the batch of refunds. Many merchants hold the batch and only finalize the batch on the end of the week. Miss the merchants weekly batch processing and you may wait a week before the process of getting you your funds even starts.
Request from the merchant the Acquirer Reference Number (ARN). Every credit card or debit card refund must have one. Give the number to your bank and they can trace the refund and update you.