This has happened to me before where this website's concerned: I log in, see "welcome my user name" at the top of the page, then reply to a post or raise a new query, click to "publish this thread" and. . .
The only thing that happens is the screen changes to the forum view again.
No post sent at all.
And at the top of the page it says LOG IN.
(Which means this post won't appear either if the same thing happens again.)