Do you have a transaction ID for the TX in question?
Do you know which payment processor they use? E.g. bitpay?
My best guess currently is that the TX is confirmed and that you need to contact the payment processor they use.
The transaction itself has disappeared from my multibit client after i did my first blockchain and transaction reset. It seems they are using coinbase as their payment processor but without a transaction ID there would be no point in contacting them with no proof.
The funny thing i tried to order the same items 11 days earlier from the uk.webuy.com website and again the payment process timed out after i paid and 11 days later they sent me a full refund in bitcoin.
This time after i paid and it timed out with 1 confirmation when i was trying to view the transaction on blockchain it was given me a transaction not found error.
ive heard something about exporting my private keys to blockchain but not sure what to do.