We have fixed over two hundred iPhone 5 pry damage phones, including dozens of International phones. Jack's was one of the first, and it is even featured in our original blog post on the topic. We sent it back to Australia via USPS First Class mail, which was the affordable option we agreed on--tracking number was only on the printed paper receipt which had been filed months before anyone recognzied that the package was lost. We did go out to storage and found the paper receipt: Tracking = LJ005217772US
I have learned quite a bit about International Shipping since then, and unfortunately International First Class is inexpensive because the post office has no visibility on the package once it leaves the US. The tracking on this package is marked Chicago, and then nothing after that. I assume it is lost or stolen since it was never delivered anywhere. We no longer ship International First class outside of Canada and UK, and we make sure that all International customers understand that there is some risk with International package shipping.
I think the USPS makes mistakes, but they usually do a pretty good job. A phone bound for Germany cleared customs in Brazil, but eventually it made its way back to Miami and then showed up good as new in Germany. We've had only three casualties out of hundreds of phone---two of these were shipping to Australia, so we now require post office pick up in Australia.
Best of luck Jack
Jessa (Mendon iPad Rehab)