Now, let's be clear on what has been said about drones striking aircraft:
1) No one has said a rotor strike would down a chopper
2) Many, me included, have said a drone being sucked into a turbine engine VERY LIKELY COULD CAUSE ENOUGH DAMAGE TO DESTROY THAT TURBINE ENGINE
I've seen rotor blades on H-3 Sea Kings after a bird was hit that were deemed unusable upon landing while others were left on for several more flights. In this case, I'd say the pilot and crew got very lucky as the blade held up and the oil cooler wasn't seriously damaged. I'd also say the drone operator was very lucky he wasn't spotted or he'd be sitting in a jail cell right now.
Just had another thought. It is very likely the drone was above the Blackhawk since, by nature, a rotor blade is pushing air downward to generate lift. That means a low pressure area is above the rotor blade circle. This means the drone very likely got sucked down into the blade arc before being struck by the blade. As I said, just a thought