[Closed] Royal Mail claims for lost stuff any advice?

I sold something on the classifieds nearly 3 week since. The item never turned up to the buyer. So after 14 working days the numptys at Royal Mail class this as lost. I got a claim foorm from the post office but looking at it it says it needs proof of original item RRP like a bill of sale. The thing I sold was a shifter and would cost about 30 quid to buy new. I don't have any receipt as who keeps all that stuff after a year.

Anyone had any experience of claiming money off them for lost goods? To be honest I have posted loads of stuff to people on here and ebay and bought stuff my self. I never had anything go missing in the past so its not a bad ratio I suppose, when you consider how crap Royal Mail is run.