If we're talking about the same thread, the thread isn't deleted. Posts prior to a specific one aren't visible in thread-browsing mode because of a post that contains HTML that interferes with viewing because of the way we're parsing a "header" out of the post. It's a bug that's being taken advantage of. I don't want to completely squash that bug, though, as it's what allows people to post charts. However, in addition to being able to be misused in the way I've discussed, it's also why the system doesn't like it if a URL is the first thing in a post.
I'll go zap the post now that's causing that, although it sure messes up my ability to review deleted posts.