RE: Finally got burned by Hobby King.
Returned mail isn't likely to go air freight. That package is probably in a cargo container somewhere in the middle of the pacific right now. Depending on how many stops a freighter makes before reaching your package's destination, it could take at least a couple of months on the surface. I've sent stuff to Australia from Florida on the surface, and it normally took about 45 days to get there.
If it arrived here in CONUS and was returned, then there was probably something wrong with the customs declaration, address, or the package was found to contain materials the carrier was unwilling to handle.
I know if you want the USPS to be reliable, using a "normalized" Zip+4 printed in a 20pt monospaced courier font almost ensures success. I've shipped 500+ packages around the world and to the USA and never had a single one go missing.