It may be that the buyer a little over eagerly opened that item not received case, as they saw the item was not being dispatched, they escalated the case, and eBay has refunded them.
You can check if the transaction was paid and then refunded here:
https://www.ebay.co.uk/sh/fin/transactions
If this is still not clear, then contact eBay Customer Services who have full access to your account and can see what has happened here.
To Contact Customer Services, I find the quickest way to contact them, either for a Live Chat, or you can select to speak and request a Call Back, to click on this link:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
On weekdays lines open between 8 a.m. and 10 p.m.
On weekends they open between 9 a.m. and 6 p.m.
@br1kem-0