After releasing the Windows 10 October 2018 Update on 2nd October 2018, Microsoft stopped distributing the update over the Windows Update channel as well as via Media Creation tool, due to users reported personal data files missing issues.
If you are one of the affected user, STOP using your system immediately and contact Microsoft support as mentioned below to help you recover those lost files.
Recently, after the users started reporting about the missing personal data files, Microsoft immediately stopped pushing the Windows 10 October 2018 Update over all channels. According to the Microsoft support website: "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."
If your files got affected due to this update, here's a good news for you. Microsoft now has a tool for you to recover your files. Dona Sarkar, in her tweet, mentioned about this tool to get you back to a good state:
If your files got deleted after upgrading to Windows 10 October 2018 Update, immediately stop using your system and call the Microsoft Support either on phone at +1-800-MICROSOFT or call on a local number in your area. Alternatively, you can contact them over chat support from a different system.
If you are not sure whether you are one of the affected users, just check your Documents folder. If you have files in it, then none of your files got deleted.