If the RTH function button on the remote did not activate RTH then the controller had lost signal to the drone. After about 11 seconds of no connection the drone should automatically RTH. The app has no effect on this other then the setting you made for the RTH. (hover, land or return to home)
As a test for this you can fly out 100', unplug the display from the controller and then press the RTH button. The drone will return according to the RTH settings you have.
As a test for this you can fly out 100', unplug the display from the controller and then press the RTH button. The drone will return according to the RTH settings you have.