Did you return it with trackable postage?
If yes then open a dispute via ebay for item not as described and escalate to a claim as soon as you can
Enter any tracking details into the dispute and if the message to return for a refund was via ebay messages then state this and copy and paste it into the dispute.
If you returned it with no tracking then you may have done your money
If you funded the payment with a CC you might be able to do a charge back but they will also want proof of return postage.
You can leave feedback to show others what has happened as well if you have not left it yet
