That's because the current mod for the FOV slider isn't just a simple mod, it has to inject things into the game files, so the game thinks its some kind of hack. When the modding community figures out how to make one that doesn't, it probably wont ban you.It didn't lose it, you can just get banned for it. Even an fov fixer can get you banned online, sucks but I don't use mods anyway so I don't care all that much.