@TerryP , @alabama mike , @bamaledge , it's a skull all right. None of us saw it while in the cave. The guy who took this picture, that's his dad in the foreground and me in the back, found it about a month later after our visit. He was looking at his pictures on the computer and found it. He sent it to me and asked what should we do? I couldn't believe it.
Between our visit and him finding the skull in the picture, the USFS had placed a moratorium on all cave activities inside the Bankhead forest because of the white nose syndrome spreading to bats in Alabama. It was a fine and possible jail time if you were caught inside a closed cave.
I suggested we notify the USFS at Double Springs and let them decide what to do. My friend did so and and asked if we could get permission to revisit the cave and they would not give us permission and warned him about violating the moratorium. So we didn't go back and I have asked the USFS about the skull a few times since but no one knows anything about it.
I'll share a few more pictures from inside the cave. It is beautiful in there.