Scammers don't usually buy £10 baths.
Somehow, the item was relisted after it was sold.
You need to cancel the sale and refund the buyer.
Click on 'view order details' next to the item in your 'sold' list and choose 'cancel order' from the dropdown menu.
"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)