I don't think we're grasping at straws, we're all just speculating and trying to put 2 and 2 together. To me, trying to definitively say the Richat Structure is "nothing" or that there wasn't a lake up there is waaaaay more short-sighted than speculating on trade routes of a 12,000 years ago civilization that had that as their capitol.
If there's one thing all of these maps do definitively show, it's that the Sahara desert was much smaller than it is now 500-800 years ago and still had some of its major waterways.