Both.
Messages are not sorted in the right order for example...

sorted by descending date i mean

If the section is called "top posts of...", then it's sorted by decreasing score, not by date.
Your thread may not appear in the live stream because its score is below your filtering level. Either lower your filtering level, or wait for somebody to vote+ for it.
Check the "new threads" section for threads sorted by date.

And, by the way, why does this thread not appear in the live stream ???