This sounds like something we discussed many years ago. I tried to find the post but haven’t been able to locate it yet. It was something about the pigment and some bunnies so have darker pigment spots even if it doesn’t match their fur (IF I am remembering this right). I know most of my bunnies I would have been able to notice such spots during combing without a problem, but my bunny Vivian has such soft, yet very thick fur, very dense, and I rarely see the skin when I am combing through it. So it could be easy to miss a pigment spot that may have always been there.
Also, a long the lines of what Jersey said, Vivian’s fur is a different colors at different lengths – the top part has dark brown/black tops, the rest is red/orange, and the fur closest to her skin is gray and then white. So if her fur were to grow out from a bald spot, I’d assume it would start out dark — making the skin look black.
I’ll keep looking for that old post — I’ll post it if I can find it!