Hey man, Don't know you but I feel for you as sort of the same thing has happened to me, just with different items, but Good luck and I hope they can work something out(the PD and USPS)
I don't know what happened, but I just completed a deal with Luis (SVT Cobra) just a little over a week ago and everything went perfectly. The shipping only took a day as I live in San Diego, he lives in Bakersfield, but we kept in touch plenty and he is a cool guy.
Reading the thread in that link, it may be possible that someone at the post office took out the amp and replaced it with clothing? //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif