Why did my homescreen delete app shortcuts?

[AC Question]

I was playing Fallout Shelter on my phone (OS - android 6.0), went to shut the app down, and when I came to the home screen, the three tabs I usually had were gone. They were replaced by just one tab with only a handful of my installed apps. Shortcuts for most, including preloaded shortcuts from when I bought the phone, were gone. When I checked the home button, all the apps were still present on my phone, but I had to re-do my entire home screen and add on the extra pages/tabs. Does anyone know why this happened and/or how to avoid it in the future?