I would imagine that chasing one of these "drones" (which is essentially a toy helicopter) using a real helicopter would be difficult, since the toy helicopter is smaller, more maneuverable, and more difficult to see. Sort of like trying to chase a bird using an airplane.
In addition, the toy helicopter would not be easy to see on radar, especially if it were to fly close to the ground.
In addition, the toy helicopter would not be easy to see on radar, especially if it were to fly close to the ground.