Demonstrate, please, that they did in fact arrive at this conclusion. “We don’t know how,” I believe is what they said. “. . . therefore God did it,” I believe, is YOUR conclusion.
Please understand that not knowing A is not the same as knowing not-A. This is a basic principle of logic.
Let’s say my dog gets out of the back yard. I check the gate: it’s locked. I look for holes under the fence: there are none. I talk to the neighbors and determine that nobody let the dog out of the yard. One by one, I rule out all the ways I know that the dog might get out of the yard, and conclude, “I do not know how the dog got out of the yard.”
I do not therefore conclude that Jesus miraculously let my dog out of the yard. That would be silly.
The shroud is a piece of cloth with some markings. The markings got there somehow, and the examining scientists have not yet been able to ascertain how. It could be an unknown technique. It could be a kind of fading in the sun at some point. It could be aliens or trans-dimensional magical monkeys. It could be Thor or the devil trying to fool us, or a saint who’s not Jesus. It could be someone who ate plants grown in uranium-rich soil.
There are infinitely many possibilities for any unexplained phenomenon. At no point does, “. . . therefore God” work, unless you have POSITIVE EVIDENCE.