It's a pity though that the folks at the L of C in Washington couldn't supply a correct photograph of John Lomax. I'm sure that wasn't him.

It's the same photo as in Wikipedia and other sources. It's obviously a young photo, and others are of a much older man, so I suppose you could doubt the provenance of the younger photo. I've never seen any other photo of the young John Lomax, though I have to say that photos of his son around the same age have a serious resemblance.