There are reports of users who already installed Windows 10 October 2018 Update (Version 1809) faced issue that their files gone missing. They might attempt using certain recovery tools but they failed. In this case, you are advised to directly contact Microsoft Support and they will help you to fix this issue. You don't need to be worry and just contact support and follow guidance of support agent. Microsoft also paused the update until issue get fixed and if you are not affected with issue, you don't have to be worry and you will only get update when issue has been fixed. Here is the official workaround:
If you have manually checked for updates and believe you have an issue with missing files after an update, please minimize your use of the affected device and contact us directly at +1-800-MICROSOFT, or find a local number in your area.
Alternatively use a different device to contact us (link will vary according to country of origin).
If you have manually downloaded the Windows 10 October 2018 Update installation media, please don’t install it and wait until new media is available.
We will provide an update when we resume rolling out the Windows 10 October 2018 Update tocustomers.
In addition, you may open Start or Cortana in Windows 10 and search for Get Help or look for it from app list and open it and from there attempt contacting Microsoft Support.
Update: Microsoft fixed the issue and released it to Windows Insiders and once it has been fully tested and there wasn't any issue, it will be released to the public , you may read more about it on:
I noticed, some people asking about problems with their updates, I am requesting those who are facing issue with Windows Update, please ask your question on forum and please Do NOT post in this discussion , since it is out of scope of this discussion we won't be able to answer here. In this discussion we are only able to help those are facing issue with Deleted Files Caused by Recent Build Update 1809 .
