A bug in Windows 10 October 2018 Update (version 1809) causes the complete removal of certain user files during the install of the new OS release.
While at this point it’s not yet known how widespread this problem actually is, there are several discussions online dissecting an issue that leads to users losing files in Windows 10 libraries and in the public folder (some examples are here, here, and here).
Judging from user reports, the glitch is encountered when upgrading from Windows 10 Fall Creators Update to the October 2018 Update via Windows Update.
Files like documents, pictures, music, and videos stored in Windows 10 libraries are deleted without any warning, and at this point, it looks like they can’t be recovered if a backup wasn’t created before the upgrade.
No fix, no way to recover lost files
Several users in the linked threads have already confirmed the problem both on their machines and on those belonging to other individuals or clients, and in most of the cases, it appears that Windows hasn’t automatically created a backup of the removed files. While a Windows.old folder does exist to allow users to return to the previous Windows version, backups for files stored in libraries aren’t included.
“It did happen to one of my PCs. Took out the SSD and attached it to my main PC using SATA to USB 3 and the drive was almost empty. I had backups, so that wasn't a big issue for me. Only thing listed was a Windows.old and the regular Upgrade folder,” reddit user SonicHyuga explains in a post.
There’s no word from Microsoft on this bug just yet, and a workaround does not exist, so we recommend Windows 10 users to create backups of their files before beginning the installation of Windows 10 October 2018 Update.
The cause of the glitch hasn’t been discovered, and it’s pretty hard to tell which systems could be impacted. We’ve reached out to Microsoft for more information on this and we’ll update the article if we get an answer.