Just a couple days back, Microsoft pulled October 2018 update due to complaints from users saying that the upgrade is deleting personal files. After pulling the upgrade from being rolled out, Microsoft created a company support document which said the users to contact them if they think their personal files are deleted. Later, Microsoft updated the support document saying that the chances of recovery would be higher if they can refrain from using the affected PC until the recovery process has been completed.
It is a well-known fact that the chances of file recovery will be higher the less you use the PC before starting the recovery process. This is because of how filesystems work in Windows.
So, here's what Microsoft is doing to recover files deleted by the October 2018 update.
What is Microsoft doing to recover deleted files?
According to a Reddit who contacted Microsoft to recover his deleted files, Microsoft is following a two-level approach. If the first level didn't recover the files, the issue will be escalated to level two.
Level one: At this level, you will be asked to restore your system to the previous restore point which is automatically created by System Restore when upgrading from April 2018 update to October 2018 update.
This generally solves the problem and the files will be recovered as part of the restore process. However, this approach may fail if you've previously disabled system restore point in Windows 10. If you've disabled system restore point or restoring the system to it is known good state didn't recover the files, your issue will be escalated to level two.
Level two: This level includes a much more thorough investigation and recovery process. This includes but not limited to a Microsoft support agent remoting to your system, scanning for existing backups, looking through NTFS file records, etc.
Do keep in mind that this approach completely depends upon your hard drive's freed sectors and files not being overwritten by the system. That is the reason why Microsoft asked users to refrain from using the affected system as much as possible. The less you use the system, the less will be the chances of files being overwritten.
All in all, if you are the unfortunate user whose files are deleted by the October 2018 update then contact Microsoft as soon as possible.