11-10-2018 9:35 AM
A bid can only be retracted by a buyer if the auction is live.
What you've encountered is called a chargeback - when the card holder reports the payment as being unauthorised by them, either because somebody has stolen their card or their account has been accessed or because they're pulling a fast one.
PayPal Seller Protection covers you against a chargeback if you have your proof of posting slip showing that you sent the item out to the address that Paypal told you to send it to. Make sure than scan or photograph this and that PayPal have a copy if it a.s.a.p.
Buyers can't retract bids after an auction has ended. They are responsible for securing their passwords, and for any unauthorised use of their account if they don't.
As regards payments made for items, payment is made through PayPal and has nothing to do with eBay.
To complicate matters further, most PayPal payments are funded from the buyer's credit or debit card. Claims of unauthorised transactions arise when the buyer tells their card issuer that they didn't authorise a card transaction. The card issuer then makes a chargeback against PayPal to have the payment reversed.
You have told us that it was eBay who contacted you. If it's a chargeback I would have expected it to be PayPal who contacted you. As another responder has already advised you, PayPal will indemnify you against chargebacks provided to can provide proof of posting to the buyer's address. The details are explained in the PayPal's agreement.
As long as you have proof of posting to the address supplied with the Paypal payment then you should be covered by Paypal for any unauthorised use chargeback