That's technically true. The beauty of science is that nothing is assumed to be the absolute truth. Even the most rock solid theory could be proven wrong one day.
Science deniers though will obviously only require proof for those scientific theories they dislike without applying the same standard to their own ideas.
If you really want to be stupidly speculative and assume that's an actual piece of an animal, you could just as easily speculate that it's, say, a condor talon.
Okay, let’s pretend it’s a thumb and not some kind of concretion. Why does it have more nails at the base of the thumb?? What fuckin anatomy is going on there? This relies entirely on you glancing at it for half a second on Facebook and seeing the right trigger words to not look at it any harder.
Also, I'm willing to buy that skin might be preserved somehow, but not the soft tissues underneath it. Not s perfectly preserved whole thing including the fucking cuticles.