Why are files missing after restarting my Windows 10 computer?

Question

Hard disks

Good afternoon.
Environment: there is an HP 15-r259ur laptop, which I immediately upgraded to Windows 10 after purchase. I have been using the laptop for a little over 3 months, and have not encountered a similar situation described below. The hard disk is divided into 2 partitions (not counting the recovery partition) (C:200, W:706 GB). The Yandex.Disk folder is mounted on the larger partition.
Situation:after completing the work, saved several files (format .docx, .pck, .sql) to W:. I immediately collected these files in an archive and copied them to the YaDisk folder. I made a public link, checked it, sent it to a colleague. Turned off the computer. The next time you turned it on, it turned out that there were simply no recent changes. Moreover, there are no files on YaDisk, even when I opened the link, I saw a message a la "file not found". At the same time, in the "Recent Documents" in MS Word there is the same file created the day before, which cannot be opened due to the wrong path.
Summary: All changes made to the W: partition were discarded on reboot at some point in time. At the same time, the changes to C: were fixed. What could be causing this strange behaviour?
Thanks

Answer 1

Somehow the state of the disk was rolled back, this is possible only with the participation of the user, although everything is possible in the top ten, the system is fresh, not rolled.
And the fact that there is no Yandex disk, so it’s clear where they will come from if you turned off your computer?