I see this from time-to-time. When the page is still loading, the default UI is that you are not following, when in reality, it just hasn't loaded.
Also, I had a 9 day post gap, so that could have added to the confusion. :D
It would be better if a) there was a neutral UI for when the info hasn't loaded yet and b) the follow/unfollow button should never be a toggle. If it says you are going to follow someone and you click it, and you're already following them, it should do nothing, not toggle.
I thought it just might be a display issue similar to how the Rep changes to 25 in certain situations. I'm pretty sure it isn't. However, not sure enough to be able to offer any evidence. :)