As Microsoft’s John Cable explains in a post on Microsoft’s Windows Blog, the problem was with the “Known Folder Redirection” feature. This is the feature that lets you move a known folder like C:\Users\Name\Downloads to D:\Downloads, for example. Other folders you can move include Desktop, Documents, Pictures, and Videos.
After the April 2018 Update, some people who had previously used this feature reported an extra empty copy of the original folder. For example, an empty copy of the original C:\Users\Name\Downloads folder appeared. So, to solve the problem, Microsoft introduced code that would delete those old, empty folders.
There was just one problem: The code deleted these folders even if they weren’t empty. So, if you moved your Downloads folder to D:\Downloads but still had a C:\Users\Name\Downloads folder with files inside it, Windows 10’s October 2018 Update would remove the original folder and the files inside it.
Microsoft has now fixed this problem, and Windows 10’s October 2018 Update should stop deleting these “old” folders full of files. But we’re shocked that Microsoft messed up in the first place. They should have only deleted the folders if they were actually empty!
If you did experience data loss, Microsoft Support advises you call +1-800-MICROSOFT for help. Microsoft retail stores will also try to help, and may be able to aid you in recovering your deleted files.
The latest version of the October 2018 Update is now heading to Windows Insiders for additional testing before it rolls out to average Windows 10 users.
We recommend backing up your files to protect yourself against bugs like this in the future.