As soon as you issue a refund, the return label will no longer be shown to the buyer and the case closes.
Of course the buyer can still send the item back. Is it an item of clothing?
I would sent them a mailing bag with your name and address and sufficient stamps on to send the item back to you.
Obviously message them first and ask them nicely if they will send it back - they shouldn't expect to keep the money and the item.
"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)