Military ships will sometimes outline names and/or hull numbers with a bead of weld to facilitate a quick repainting of the identification. If NC had done something similar, the bead would be decipherable long after the paint was gone, or at least faded to the point were it wouldn't show up in a photo. Lighting and contrast can lead to lots of things playing hide and seek.
If they actually didn't know where they were (I've posted my doubts on this in
another thread, they would be highly motivated to ID the ship. Burnt or not, I find it hard to believe that there was nothing on the wreck or the shore that would tell them the name of the ship, especially if you accept the theory that they could only transmit during windows around low tide, thus forcing lots of off-air time on them.
Life rings, jackets and other survival gear are often marked as well as boats and rafts. Also ship's equipment that was pilferable (sextants, anyone?), etc..
Grave markers from the crew who were buried there?
Whether or not someone
could do something in 1944 doesn't tell us anything about whether someone
did do it in 1937.
What do we know about the lifeboat equipment? Without a mast and sails, FN would have been just meat in a frying pan hoping to get lucky and that's not much of a plan. Given the
water question, it's hard to imagine a rational man taking those odds. Then again, maybe some Antarctic cruise ship will spot something in a thawing glacier and we'll end up with the 4th boat, misssing sextant, Zippo lighter and the navigator to boot.