http://www.techradar.com/news/windows-10-fall-creators-update-hit-by-bug-that-causes-apps-to-disappear

Another problem has popped up with the Fall Creators Update, with affected upgraders finding that some of their apps are disappearing from menus in Windows 10.

Those hit with the issue have found that the icons to launch some apps have gone missing from the Start menu, and neither are they to be found on the operating system’s list of installed apps. A Cortana search won’t locate them, either – even though the pieces of software in question are still installed on the PC.