Was it truly a survey line Guy or perhaps a gun club cut line ?It was really deep but on a cut survey line. It could have been worn by those cutting the trees.
Most clubs maintain lines through the woods for breaking the large tracts into smaller drives. Most of the locations are handed down from generation to generation and their beginning points are hard to pick out from the main roads. I hunted with a club in the 80's who had miles of lines cut and no one would ever know where they started. Once you were on one, Ray Charles could follow it.
The missing guy was a club hunter according to the original accounts.