USPS First class international mail tracking?

USPS First Class International mail does not offer any tracking. We issue a customs ID number which confirms the following
1. Give you proof of shipping since we only get that number from USPS when the package has been shipped. 
2. Allow USPS to have a mechanism to deliver the package to the Postal Service of the destination country which then takes over the final delivery within the destination country. That is why there is no tracking for international.
Because the package is in the hands of the postal customs agency of a  sovereign nation, there's really no way for us to get a package released or shipped back. It depends solely on the policies of the postal customs agencies of various countries as to what they do with the package if it is unclaimed.