Right, an unclaimed payment that cannot be cancelled is a payment that has been made to an active PayPal account but the seller has to manually accept it, either because they have to accept all payments manually (unlikely) or the payment is in a currency they don't have a balance in (most likely the case). They have 30 days to accept it or it'll be automatically refunded back to you.
Really the best thing you can do is send them a message letting them know what e-mail address they're after invoicing you with and seeing if they can accept or deny it manually themselves.
