Not really sure what you mean. Sometimes threads get buried when there is no interest, and other threads take over near the top ... Are you talking about that, or about some threads maybe being removed? Clarification???
Well it might seem that way, but if there is a lot of people posting, then there will be post that you see today that might be buried within pages. You should probably just check them and see the post you were looking for if that's the case.
I did that the other day looking for my post to see if someone responded to it. There were some replies, but I had to go search for the post.
I think they are right. Maybe the post you are looking for didn't stir up any interest and it got bumped off the top by other more interesting topics. Which one is it that you think disappeared? Just out of curiosity...