That's utter rubbish, Jerry...and you know it because you've posted many photos that show the bright sunshine in that area.
Boone said he saw the Carcano about 1:22. You would need the sun to be almost shining straight out from the West side to directly illuminate the crevasse where the rifle was found. About 1:22, the sun was shining on both the West and South sides equally. At 2:30, the sun is still not shining from fully onto the West side.
Day had to examine the rifle beside the window to better see it. You just said flashlights were needed. I think the light-bulbs in the ceiling were pretty-low wattage. I would guess they weren't just looking for the rifle; could have been small things as well, anything suspicious.