I finally met a car load of the mysteriously mythical lost people. Last night a car pulled up along side me on ridge road, heading for mount dandenong. The man driving asked for directions to dandenong city. After some discussion to confirm that was where they really wanted to go, I directed them back down to the mount dandenong tourist road and thence to the burwood highway, they seemed then to know where to go from there.
I guess people are driving past, see the signs to mount dandenong and head off in the wrong direction.