There is an app store update problem, both on iOS 9 and 9.0.1. Several apps never complete an update, either they freeze at halfway or 100%, you just see an "installing" under the app icon for two days. And if you reboot the phone, those apps are deleted from the homescreen, Settings app show them as ghost apps (screenshot attached). The only way to find these ghost app is to guess them from the "purchased apps / not on this iphone" list and download it again. 100s of apps to scan, and you have to know if they were already installed last week! UPDATE: I connected the phone to PC. I have 3 home screens, but iTunes showed a 4th one which includes the ghost apps and some other recently deleted apps. I re-installed them from ipa files in the iTunes archive. Ghost apps are gone from the Settings, well this may happen again, keep an eye on what you're updating.