The sender is the one that has proof it was sent.
Recorded and Special delivery have different terms of cover. Recorded is only tracked when it is recieved and "signed for". To confirm delivery go to click here.
Where as special delivery is guaranteed next day (or your money back) and is tracked at every stage as it goes through Royal Mail's network. If it's special delivery you can phone the customer number on the back of the silver coloured reciept and they should be able to tell you exactly where it is!