It's worth keeping in mind that drones such as the DJI Phantom can also be flown on Waypoint mode. This means that the drone can be both out of LOS (line of sight) and beyond FPV (First Person View) video range. The operator can set up a chain of waypoints, upload them to the aircraft and send it flying. The ground based equipment can be turned off while the drone does its thing autonomously.
Such a drone could enter the airspace that the helicopter was practicing in after the helicopter pilot had done his checks and started his manouvering.