I am sure, that no one did this today. This is my authority.

But for this problem I found a very unusual cure:

I limited the grouth rate of tempdb log by 50Mb at a time. Once it reached 99%, it was grown by 50% and then freed up about 97% of space. So now it is 8Gb (as before) and 14% used (filled up a little again)

I still cant understand why the log is not truncated...