I was sent a package by a sponsored source with over $1K of product using USPS Express Mail which the postal service appears to have lost. Source says the package was insured so I can file a claim. USPS wants all sorts of information like a receipt or some proof of transaction, which of course I'm not going to give them for obvious reasons. I'm not familiar with package insurance payable to addressee so this is a new one for me after years of buying gear online. Anyone here ever had to file one of these claims in a similar situation? Especially would like to know how others have handled the receipt or proof of transaction part.