Those tiles may have just been "unpinned" from the Start page. Leo says he can just start typing the name of the app in the Start page, and it will launch a list of all the apps. It will either jump to that app right away or he can find it with his mouse. Then once it comes up, he can "pin" it to the Start page. Wendell says when he types the name of an app, it says that no apps match his search query. Leo says he'll probably just have to reinstall Windows 8. It is just a preview, and there still could be some unexplained issues.