This member could have paid the incorrect email address through PayPal. On their end they would see "Unclaimed" if they logon to PayPal but they would have originally gotten a receipt for the payment. Happens all the time on eBay.
Have the person logon to their PayPal account and check the history. The payment is likely sitting in cyberspace waiting for them to cancel it. It will return to their account in 30 days if they don't.
A simple mistake like putting .net instead of .com for your email will cause this, or even an extra space. PayPal uses email addresses like account numbers. They system that triggers the receipts and emails is less sensitive than the one that transfers the money.
