There are specific times to follow when opening a return case, it's not open for many months, and will close from inactivity.
Once you saw the item was returned to the seller, they had 48 hours to refund you. If they didn't, sending them messages doesn't help, you had to escalate , which you did not do, so the case closed.
You cannot open another for this with eBay and will need to turn to your payment provider for help with your refund now.
@craigr586