This is not a wrong turn scenario to end up all the way up by Moorestown. M-55, the state highway runs from Prudenville to Cadillac. It's not a hard route to follow, also her living in Cadillac means they knew where they were going. The drive is not that far. I lived between Lake City and Prudenville growing up. What is plausible is that they went two-tracking for fun. That is what people do around our area. They most likely went up there to do that and got stuck. It is possible that they were pretty deep in the woods that they couldn't get back to a real road walking.Thanks for posting this map. IMO is shows how this could easily have been a wrong turn scenario.
It is not a wrong turn if you purposely drive off a real road onto a two-track.
This is written to give factual insight into implausible scenarios and speculation.