First, next time you choose a vendor to do business with, do your homework first. There are quite a few people here who will be not at all surprised with your outcome.
Did you obtain a specific Return Merchandise Authorization from the vendor?
Next, when you ship a valuable item, spend a couple dollars to cover your own ass. Insurance is a couple dollars, and I believe has a signature requirement, which you needed.
You may be pressured to make no public disclosure of your experience. If this does occur, and you are unhappy about it, please please pretty please share this event here, and I personally will be ecstatically happy to help you deal with the issue effectively so that you are made whole in this transaction, at no charge to you.