Road 670/671...

Many of you have already heard this and are sick of it, I am too. But this is really bothering me, for the life of me I cannot find this final road. I've skimmed the enite map looking for the fast travel button to dissapear, ive done the events that take me on every single road in the game but yet im still missing one somehow?!? Any tips would be greatly appreciated. I am going to redo those events again to try to find the single pixel of road i have missed..