Hi, Seed, good to see you.
That happened to me. I clicked on contact us (see at bottom of the page) and addressed my problem to Jespah, and she helped find the missing material. I am assuming it happened in some sort of a2k site maintenance thing and I didn't notice it for a long time, maybe years. I've no idea if different post losses have different causes, but in my case it could be found.
It wasn't easy for her to find it, and I think it would help if you give her the specific details of the thread URL and title, and the URL of the first post that you do still see. That's the number to the upper right of where your avatar and screen name are.. right now, for example, your post that I'm responding to is #4,710,186.
Be patient - if she or another mod can find it, it may be time consuming to do.