Hmm...I would use my bank records then to show them I did indeed purchase it. Amazon has just a great track record. If nothing else you could do a snipe of your online checking or cc account and erase out any too personal of info and send that to me. Bet that would work. Still, I have never had an order disappear from my order history. Between me and my wife I bet we probably have ordered a few things from amazon for years now.
Woah! Spooky beat me to the idea I had.