Order from TCGplayer lost, unsure what to do

Title, not sure if this is the right place to post this, though first time this has happened, and I don't know where else to ask.

Ordered a card around $50 from a seemingly reputable seller. To their credit, they did get tracking through USPS, which showed as delivered. However, a week has gone by and I've yet to locate the delivery.

I've already opened a case with USPS, but after their investigation, they still hold onto their claim this has been delivered. I checked in with my residency's management, though they weren't able to provide any further help.

So I contacted the seller, which I asked for guidance or if perhaps there was insurance purchased so I may file a claim to USPS having potentially lost it. Unfortunately the tone of the reply from them felt aggressive and had me discouraged on getting their assistance any further.

My final two options I have are either to try again with USPS's customer service to see if they may conduct the investigation once more, if not have TCGplayer step in.

Anyone have experience on the matter and are willing to share what they did would be greatly appreciated.