windows 10 (October 2018 update) (version 1809) deleted all my files

Maybe others have already replied with the same thing. What happened to me was that the entire C:\Users<profile>\Documents folder was moved to OneDrive.

Before the October update I had files stored in the local Documents folder, mostly different kind of log files. After the update all files have been moved to C:\Users<profile>\OneDrive\Documents leaving the local Documents folder empty.

If you haven't checked already, you should have a look at your OneDrive regardless if you actually use it or not.

I have problem with onedrive from ver 1807. I contact with sp microsoft but they don't slove my problem. And ver 1809, a lot of people lost file with onedrive :V

Trying to work out from your pics where the update moved your books folder. (Updates shouldnt even be MOVING users data folders let alone deleting them!)

Its not clear but your books folder is in the /user directory (the area of concern), correct?

The links had been removed?(like feature update 1709)

The books folder moved, where did it move to? Was it hidden?

So all you had to do was create a new shortcut to it?

UPDATE: Version 1809 pulled from Media Creation Tool as of 9:52 PM PST Friday. I think it might be due to this issue since we've heard nothing on it from Microsoft yet. 

The Version 1809 Update has been withdrawn.  If it's pending here's how to abort it:How to Cancel Pending Installation of Windows 10 Version 1809.

If you have it installed you can roll it back if it's causing problems at Settings > Update & Security > Recovery, or wait for corrective Updates to be pushed to solve reported issues.

A report here today that files were found in online OneDrive Recycle Bin feeds one theory in my possibility checklist at the beginning of this thread that OneDrive has force-enabled in it's Settings for many users Files On Demand so the files only live in the cloud and are only chosen to download from links on the hard drive.  This should be only a consumer-selected extreme space saving measure,

Then add to that the File Protection sync selections in OneDrive settings Auto-Save tab are force-enabled for Desktop, Documents and Pictures folders,

So if those folders now only live in the cloud and an Upgrade occurs, where are they sync'ing to afterwards, if at all?  Maybe into the Recycle Bin.  So check there.

Windows Update can ONLY update. It cannot remove your personal files and folders without being instructed to do so. This is not hard to comprehend, I hope.

Now you may have malware or hardware problems that have caused files to suddenly disappear. Anything from a Trojan to a hard drive failure.  You all might want to run some checks to see if any such issues show up.

You can begin by running the Windows Memory Diagnostic:

You can also open the Command Prompt (CMD) and run SFC /SCANNOW as well as DISM

Just copy and paste either of these commands in the command line:

DISM.exe /Online /Cleanup-image /Restorehealth

DISM.exe /Online /Cleanup-image /Scanhealth && DISM.exe /Online /Cleanup-image /Restorehealth

The second line runs two checks and repairs consecutively without further input from the user.

Also as I previously suggested check C/Users for missing files and/or folders thusly:

I should mention that my "Books" file (where I keep all my pdf files) had apparently vanished with the update since it was not where I had left it. At least, the shortcut was useless. But I soon located it and pinned the new location to quick access.

I like knowing where my books are 😁