Once the buyer has won a case for an item not received, they will be refunded. If Ebay refunds, they will expect you to pay them back. They won't try to get the money back from the buyer. That is not how the system works. It might seem unfair but it is what you have agreed to by selling on the site,
If the item is subsequently delivered it is then between you and the buyer.
Some buyers are honest and ask how they can pay you and some just ignore messages and requests.
If the buyer says they will return the item, send them an envelope with stamps and your name and address on so they can send it back to you. You can't know for certain they will do this.
If it was a cheap item, personally, I would just forget about it, block the buyer and move on.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)