Yep, annoying I agree, I'm sure many sellers have found themselves in this position, but that's what we , as sellers, sign up t, under eBay's 30 day MBG, Money Back Guarantee policy, sellers do have to pay for the return tracked postage when a case for item not as described is opened.
What you can do to recoup that loss, is to add it to a few items starting prices when you come to list.
Block that member too from returning if you haven't done so already.
https://www.ebay.co.uk/bmgt/BuyerBlock?
@benyb888