So, a week or two into windows 10 I got this 'interesting' situation.
One day after the startup I found that drive D was "the disk structure is corrupted and unreadable".
I ran check disks etc. and then i got to the no access stage.
Finally I took ownership of my disk.
Now I have everything back except the most important work folder I actually need.
I've tried running recovery programmes (recuva) and, well, adding ownerships. But I failed.
Maybe it has something to do with the fact that one of the folders is a google disk and got a different owner?
P.S. And, yea, it is not hidden, duh.