Restore your iPhone. If none of the above steps work, you can try restoring your iPhone from a previous backup. This will revert your device to a previous state and may bring back the Settings icon.

Kurt "CyberGuy" Knutsson gives a step-by-step "Find my iPhone" settings setup that you can do on your iPhone so you aren't scrambling ... Be sure to select the "key" icon at the bottom right of ...