Over the last couple of days, some users who went ahead and installed the Windows 10 October Update have complained that it deleted personal files in their documents folders. Microsoft hadn't started pushing the update automatically via Windows Update yet, and it looks like that may be delayed since, as noticed by Techdows, it has removed the update from its download site.
Currently the newest version available to download is the old October update, and there's the following message on its support page.
We have paused the rollout of the Windows 10 October 2018 Update (version 1809) for all users as we investigate isolated reports of users missing some files after updating.
Over on Reddit, posters have found that you can still download 1809 if you absolutely must have it for testing or just curiosity (make sure your backups are current first -- you are making regular backups, right?) from this link. This is a troubling trend for Microsoft, after it also experienced issues with the Spring update earlier this year.