Sounds like a case was opened if the seller provided the return label, if not , open one now, enter those tracking details, and on receipt of the item it gives the seller 48 hours to refund.
Once eBay notify you the refund is made, being processed, then it's not instantly returned to you, and does go back to original payment source.
If you paid with PayPal it goes back to your PayPal account fairly swiftly.
Paying with a debit / bank card? Can take up to 12 days to appear back in your bank account.
Credit card payment? This takes the longest, up to 30 days to appear back in the card account used.