I am no expert or authority so take this as my opinion/belief of how it works. Your posting privileges can be blocked on a particular thread, but I don't think that means you can't see it, only that you can't respond to it. In the cases I have seen where a thread has completely disappeared is when the person was found safe so the thread was removed, or for special reasons(like family asked it to be taken down)a thread had to be removed. I highly doubt you were banned from seeing a thread but to check and be sure, log out and view the site as guest. See if you can find the thread as a guest.