He shipped it and you refused to pay for it to register. I don't think the seller should get knocked because the package went missing. Sorry to say but I believe you are shit out of luck there buddy. If I was you in the situation, I would count it as a loss unfortunately and a lesson to learn on.
Even my last big ticket item that I bought from this forum which should be shipped out in a day or two. I actually threw in an extra $5 so I can get a tracking number.
That's the thing, do we know for sure he shipped it?
That's the gamble but yeah I do see the buyer being most at fault here.
As a BIG seller, I always insure the items I sell to people mainly because I want to cover my sell.