back button in settings disappeared
iPhone 6s, iOS 9.1, back button, 9.1, settings
It may be a bug. I'd recommend reporting it to Apple.
https://www.apple.com/feedback/
Also, try resetting the settings on your phone, this may help.
Alternatively, you may go to Settings - General - Reset - Reset All Settings
https://support.apple.com/en-us/HT201559
back button in settings disappeared