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

On my end, on the computer that was trashed, OneDrive was disabled on start-up, and was still disabled, just now, when I checked it, so it doesn't look like it automatically restarted on my end. 

I don't know if there's any connection, but I am mentioning it, in case.

I prefer to store and backup files locally, rather than on the Cloud, for security concerns.

That's what I wanted to say. Unfortunately, Robert is missing 220 GB - & OneDrive only holds 5 GB unless more was purchased. (Can it be MSFT gave him the extra real estate & plans to send him a bill?) But maybe the upgrade did the following automatically.

Before my upgrade to 1809 (still in 1803) - I had set Desktop, Pictures, & Documents to go to OneDrive. That's at "OneDrive Settings, Auto Save tab, Update folders button".  That moved the contents of those folders from C:\Users<Username> to corresponding folders in C:\Users<Username>\OneDrive. The C:\Users<Username> folders remain, but are empty. Any content previously in any of the OneDrive folders also remained, was not wiped out.

This is an interesting point, I use Onedrive. In my case there are some files from the  c:\users%username\documents in the C:\Users%username%\OneDrive\documents folder (and synced online). I don't know how much of the original folder it is and if it was there from before before 1809 or not. However, I do know that the VM file actually really miss of over 100GB isn't among them.

(1) What you said on page 3 about C:\Windows.old...

"

The C:\Users\kay_h\Documents folder was empty

The C:\Windows.old\Users\kay_h\Documents was removed or didn't exist before

The C:\Windows.old\Users\kay_h\ profile was nearly empty basically only contained some C:\Windows.old\Users\kay_h\AppData\Local data. It does have a NTUSER.DAT with the timestamp of the upgrade tot 1809. 

"

I noticed that to be true of 1803 as well as 1809. I don't know how a revert to previous version could possibly have worked (& restored user files). In both cases, a revert was/is not necessary for me, thank goodness.

(2) If you never personally changed the location of your documents folder while still 1803 (either the way I did or the other way), then it must have been 1809 that did it. It must be the default setting for 1809. That is a sad circumstance, considering OneDrive is normally only 5 GB in size. Those with more than that before the move appear to lose it all.

But later in this thread AgingAardvark56 suggested to look in the online OneDrive Recycle Bin to see whether the excess ended up in there. Did you look? Right-click the OneDrive icon, & select "View online".

Similar but not identical issue. Did the Oct update and randomly two Outlook files the where on Onedrive were deleted. No trace, not in recycle bin, gone.

Support request raised with MSFT, but pas at time of writing they didnt have any ideas

Somewhat similar, but in this update it deleted ALL of the files in My Documents on my local hard drive. No warning, no nothing. Just GONE.

I've been working for about 12-hrs, now, trying to see what I can recover from other sources and backups, but this is really a pain.....probably going to be a LONG WEEKEND..... 

I definitely would not recommend anyone else update, unless MS figures out what is causing this, so it can be avoided. 

As I stated in earlier posts, the update worked fine on two computers (I "think") but totally trashed all my documents on another -COMPLETELY EMPTY. On top of that, it trashed my restore data, so now I'm fighting with my backup.

Somewhat similar, but in this update it deleted ALL of the files in My Documents on my local hard drive. No warning, no nothing. Just GONE.

I've been working for about 12-hrs, now, trying to see what I can recover from other sources and backups, but this is really a pain.....probably going to be a LONG WEEKEND..... 

I definitely would not recommend anyone else update, unless MS figures out what is causing this, so it can be avoided. 

As I stated in earlier posts, the update worked fine on two computers (I "think") but totally trashed all my documents on another -COMPLETELY EMPTY. On top of that, it trashed my restore data, so now I'm fighting with my backup. 

Before you keep using the hard drive, you can try some recovery software to scan the drive and recover what it can. If you have an SSD where TRIM ran already, then you're out of luck.

I bet this is Microsoft trying to give people a good kick in the rear to purchasing more OneDrive space so they can make more money and access all your files.  ;)