Ray Rob was created after Lewisville, so I doubt all the Blues in LV came from Ray Rob.
like Tom said, nature has its way and some folks help along the way. Gators show up in strange areas as well.
Muzzlebrake, that is a good spot up on the Red, Above Telephone. I have spent many a day by Lake Fannin, and walked all the way back to the river on the TypeII land there.