Sorry for your loss

You can file a claim at USPS on-line right here:
https://www.usps.com/ship/file-domestic-claims.htm . I kinda went through the same thing - my entire box from HHV didn't show up. It took me 3 appeals and I received a check from USPS. Because I could prove that there was a delivery of a different box from a different company on the same day - I fought it hard. My claim was for $54 and the package only had $50 for insurance. USPS cut a check for the full amount.
I am not sure how USPS will handle a "Damage" claim. I haven't really looked into what is considered "Damage" or whatever. I will say one thing, HHV is on the outside of the shipping/damage customer service stuff. Most other vendors will re-ship, while filing the insurance claim VS making the customer jump through the hoops. I had ordered from another
juice vendor, and one of the glass bottles had the dripper punctured, and about 50% of the juice leaked out of the top. I called the vendor and the replace the bottle free of charge. I am unsure if that vendor filed a claim with USPS, the vendor did not ask for pictures or any evidence. Maybe other vendors have a better way of tracking abuse vs what HHV uses to track orders - just a thought.