Shroud of Turin

[edhopper]

70. The problem isn't missing works

as you describe, but there is nothing in recorded art history to show that anyone anywhere developed a photographic process this early.
Your theory that an isolated genius developed this process in Lirey, France, and then disappeared, leaving only the Shroud as a single example, and then it was lost for 500 years is problematic, to say the least.
You are also making some giant leaps considering a cloth that size could even be used for a phototype image. A pinhole, without a lens, could never focus an image that large, and the cloth is hardly the hard, flat surface needed.
That it looks like a photo negative is due to the rubbing process.
Why you have a hard time accepting this reasonable explanation, and trying to supplant it with a much more highly speculative, and problematic one is questionable.