i'm wondering why certain threads when clicked, gave the "no posts exist for this topic" message.

where have all the posts gone?

Sometimes the posts are deleted for whatever reason...by a moderator or if the OP asks for them to be deleted. Other times, it's a computer glitch and that thread may be available another time.

A lot of posts and threads got lost forever when the site had a crash a while back.

thanks for the responses!

Thanks for asking this question. Sometimes I'll be watching a thread with no disagreeing on the topic...just helpful advice and I'll click to look at it and it will say that. It's frustrating and I've always wondered what happened to it.

The ones that were lost in the crash can sometimes be reached by going further back in the thread. Many have just lost the last page. I try to bump them when I find one like that.