>> So which is it 'luck' or the working of God... Personally speaking I would be 'red' in the face had I been in charge of this piece of cloth and I had picked a portion of it that would discredit the authenticity of it, and I would not be blaming God.<<
Both. Where do you get the idea that it was 100% one or the other? There are significant portions of the shroud which were damaged. They happened to be in places where the image wasn't, the non-essential areas. Maybe that was just good luck, also, but it makes sense that the shroud is a miracle, than preserving the shroud may also be miraculous.
But the bishop selected a region of the cloth where the shroud had been damaged and repaired. Since much of the non-essential region of the shroud had been damaged, simple dumb luck is sufficient to explain how he happened to pick an area that had been repaired.
There's no blaming God involved, and frankly, I think you're being quite silly and unreasonable to read that as me or the bishop blaming God.