A drop in threads and posts?

Hey everyone.
I know we all have our own way of using the site forums and what not. I myself like to look at fresh posts when I'm here and revisit past threads that I've been involved in.
Well I was looking through my posts, and some topics that I've been looking forward to revisiting are, well, gone?
A locked topic doesn't just vanish, and there was nothing racey or disturbing about the ones I'm looking for.
I also noticed that some threads that I've been involved in have had some recent posts vanish, with the number of posts dropping along with the mullings of members?
Anyone else notice this, whats up with that?
I know we all have our own way of using the site forums and what not. I myself like to look at fresh posts when I'm here and revisit past threads that I've been involved in.
Well I was looking through my posts, and some topics that I've been looking forward to revisiting are, well, gone?
A locked topic doesn't just vanish, and there was nothing racey or disturbing about the ones I'm looking for.
I also noticed that some threads that I've been involved in have had some recent posts vanish, with the number of posts dropping along with the mullings of members?
Anyone else notice this, whats up with that?