@paracite
Okay -- here's the official USPS instructions --
Claims for Loss or Damage
If your insured mailing has been lost or damaged in transit, you may file an insurance claim:
Online: Go to www.usps.com⁄help⁄claims.htm for information on USPS domestic insurance.
By mail: Call 800-ASK-USPS (800-275-8777) to have a claim form mailed to you. Send the completed form with all other required supporting documentation for loss or damage of an item mailed with insured services to the address printed on the form.
Evidence of Insurance
You must retain evidence of insurance for your claim. This includes evidence that insurance, COD, Registered Mail, Priority Mail, or Priority Mail Express service was purchased for the mailed package. For a detailed list of acceptable evidence, see “General Filing Instructions” in Mailing Standards of the United States Postal Service, Domestic Mail Manual (DMM) 609.
Proof of Value
You must submit proof — such as a sales receipt or paid invoice — showing the value of the article when it was mailed. For a detailed list of acceptable evidence, see “General Filing Instructions” in DMM 609.
For Internet transactions conducted through a web–based payment network, provide a computer printout of the online transaction identifying the purchaser and seller, price paid, date of the transaction, description of the item, and assurance that the transaction status is completed. The printout must clearly identify the web-based payment network provider through which the Internet transaction was conducted.
Proof of Damage or Partial Loss of Contents
You must retain any damaged item, packaging, and all contents until the claim is resolved. If you receive notification from the Postal Service, you will be required to bring the item, packaging, and all contents to a Post Office.
