That happened to me once. It wouldn't let me delete what was already typed in there so I couldn't respond in that thread anymore. It was still there days later. The only thing I could think of was to just post my half written post to get rid of it.Yes, when I go to the "Forum" and that particular thread I see only one page of entries with the last being last Friday by Arvada. When I go to my Profile and "Postings" there are two pages of entries with several others (besides my own) that do not appear when I view via the "Forum".
FWIW in case it has any bearing.......there has been a time or two when I prepare a post but never complete it (or enter it) but when I go back later to that same thread my earlier prepared post is still there in partial form at the page bottom just as I left it when I closed out of the website. It doesn't go away. Also have been wrestling with Shockwave Flash (with Chrome) at times if that might have an affect on all this.
Hmm...not sure why that would happen. Like i said, when I click on your profile and go to your activity, I see the posts you made. When I click on one of those posts and go to the actual forum thread, they show up just fine for me. I'd suggest logging out of HN, clearing all your cache / cookies, closing your browser, then starting over from scratch. See if that helps.