Perhaps what you have experienced is due to clicking on a thread title in the "New Messages" window which carries a name different than that of the thread to which it is posted (as I have done here). Then, when you try to find that posting again on the "Forum Home" page, it has disappeared. Even worse, it will not be retrievable through a thread search (at least, I think not) under, the word "invisible" because that isn't the proper title of this thread.