@Tokyoracer
Did you pay for the postage using a debit card?
If so, you may be able to get the post office to trace the transaction, (you can find out the time and date of the transaction from your bank) and hence (assuming it was recorded) the tracking number.
Personally, I always use recorded delivery, always e-mail the tracking number to the buyer, and always keep the receipt until after they confirm receipt of the item. That way, even if I lose the receipt, I still have a record of the tracking number.
I realise this is no help at this point, but £10 is a small price to pay for such a valuable lesson - it could have been a LOT worse.
Regards
Rich
