Had a similar thing happen back during the height of Covid. Had two paid D1 tickets that the credit was never visible on. The agent insisted they could see them, but after pressing for a supervisor, they magically appeared in our accounts. For piece of mind, I would call back and at least speak to a supervisor. But at a minimum just keep careful record of the ticket number (starts with 006) as that should be number for the credit.

Note that if at some point you use the credit and still have some value left over, it will generate a new credit number to keep track of (also starting with 006).