You also can't change any assets in the config.txt. This does not work. The assets reference is kept within the route data files. What's listed in the config.txt file is for something else that I can't remember at the moment. Shane or someone else can fill you in on that.
Generally when a track shows up missing, it means that it is either faulty or the route you've downloaded a route meant for a higher version than you have installed.
John