When a message is sent, it's sent to a TNObject. If both scene's objects have the same exact IDs, it'll work fine. But if scene A has that script on object with ID of 1, and another with ID of 2, it won't work.
In any case, I suggest making it travel from scene to scene along with your TNManager. You can just make it a child of that object. Keep in mind though, TNManager's presence is not required from the start.