Sorry you feel that way.
I came to that conclusion AFTER reading up on the issue and found that a bug in ota software updates on all Android phones will once every now and then, eventually throw up this bug.
The actual solution is to open up ADB and enter the following code:
adb shell am start -n com.google.android.setupwizard/.SetupWizardTestActivity
This will cause the phone to go into the Google setup mode which will first bring back the taskbar, then on reboot, the buttons.
However, the buttons may still disappear again if whatever caused the corruption in the Shell OSD UI, happens again.
This led me, along with the fact that you confirmed it also happens in safe mode, to recommend bypassing this solution and just rewriting the software, eradicating the corrupted file and replacing it with a new version via repair installation.
As you have no access to a pc, you can copy any important files you need to an SD card and then perform a factory reset, I know this is not what you would prefer, but in the long term will be the better solution for your issue.
http://www.androidjunkies.com/how-to-fix-missing-soft-keys-and-notification-bar-after-android-update...http://www.androidpolice.com/2014/08/07/how-to-fix-missing-home-and-recents-buttons-and-notification...