...what happened?
I can't see it anymore

How about this: http://www.lfsforum.net/showthread.php?t=22900

It's hidden, but still there. Locked too, so no one can post anyway (incl. moderators).

Visible again now W10 is out...

Looks like it's being made available/hidden as & when required.

Quote from W1LLSD4D :

Looks like it's being made available/hidden as & when required.

correct

Reading most of the people there, test patch forum will be closed soon again....

Quote from W1LLSD4D :

Looks like it's being made available/hidden as & when required.

It gets closed when useless and irrelevant posts flood the threads making it difficult to find the posts that have something relevant to the test patches. It is not difficult to read posting rules in that subforum and use common sense whether one really does need to post.

There's been enough discussion about the test patch forum lately. It's there so long as there is something relevant to read, that applies to both regular forum goers and Scawen.