Once in a while, stuffs happen. I once ordered a BO Rebar, only to have an empty tool box, rewrapped, and a note acknowledging the damage during sorting. I contacted the seller for money back, leaving him to deal with the USPS.
If I were in your shoes, I would take the issue to the seller first, since it looks like the packaging was inadequate. A couple rounds of tapping around the envelope would have avoided that.