I once bought a supposed 2016 Cervelo R5 internationally on eBay. To be fair, it was a Cervelo with the Cervelo seriel number even. What it was not was a 2016 R5. It was a prior year lower model painted to look like the much sought after 2016 R5. The wrong frame shape in the bottom bracket area, the way too heavy weight, & the far too thick too high gloss clear coat over the wrong color red was the tell. That and the cut & respliced together steer tube.
Even if it is a genuine Pinarello, it could be a misrepresented Pinarello. In which case you could be safe & fine. Just a little ripped off. In any case, a replacement fork for piece of mind wouldn't be the worst thing in the world.
I wish you luck in a better than expected resolution.