Was it the M&S top?
That was listed with Simple Delivery so the buyer pays the postage directly to Ebay.
You can see a breakdown of money received and any costs in 'orders' and 'order details'.
You should have got £5 for the sale (£2 for the cheaper top) and labels from Ebay to post them.
"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)