How do you know the item has been lost?
If you sent with Ebay Simple Delivery and the buyer opens a claim, Ebay will deal with it.
They will refund the buyer and you will keep the payment for the item.
I don't know if you checked the types of accounts available when you opened your account, but sellers who use accounts to trade and sell items they have bought specifically to sell need to have a business account.
Details here:
https://www.ebay.co.uk/sellercentre/selling/create-ebay-business-account
"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)