so as in update, the seller has been very responsive in this situation. I have relayed all the info to him through emails. All of which he has replied to quite timely.
It has already been established that the seller was not in it to scam me, but it was rather a usps fault in them misdelivering to some other address or unit.
As a result of this, I have politely requested that the seller/sender file a claim with usps to get the insured 50$ back. And that I requested we split the losses.
The sender has replied back with offering me 3 pieces of his collection that he was not able to sell.
To me, this is a very generous offer and I accepted. I really value his willingness to work with me in such a shitty situation.
This time, he is shipping with FEDEX and with signature!
I'll keep everyone updated as things progress.