Most likely the control signal was intermittend and never completely lost.
You can always tap the Home button on the screen or turn yourself with the controller 180° around so your body is in between the drone and controller in order to make sure the control signal is completly lost and RTH will kick in.
Have a look at the video in this topic where the drone is hovering because of intermittend control signal (timestamp 3:55 - 5:10).