Send the buyer a polite message asking them to check their other purchases as this wrong item must have come from another seller.
If the worst comes to the worst , and they open a case for item not as described, you will have to accept, and refund as cases are all automated, no human contact. Then, you appeal the decision , and I won't lie it's not easy.
This explains how to appeal:
https://www.ebay.co.uk/help/selling/managing-returns-refunds/appeal-outcome-case-seller?id=4369
@shaunakni0