USPS leaves insured package on porch, no signature, stolen

I sent a computer video card to my son in Waco, TX and insured it for $100. The carrier left it on the front porch 30 feet from the road, did not get a signature as required, and it was stolen before my son got home from work. A report was made to both the police and the Post Office. I submitted an insurance claim with all the supporting information (and all the details are confirmable) but the claim was denied. I submitted an appeal, along with a letter from the local postmaster confirming all the details and recommending approval, but the claim was again denied. It appears that because of the malfeasance of the postal service, I am out not only the video card, but the postage and insurance fee as well.