I think it may have been a one (or 2) off bug. The first time I went into the new forum the thread loaded the mobile version. Other threads were okay. Back to the thread, same thing. Not happened since I'm happy to say, but I can't remember the thread in question now typically.
You actually caught the system in an in-between state, when the auto-switching for the iPad was incorrectly set. That should not reoccur again.