Coming from a family of pilots many of whom are heli pilots, myself I'm fixed wing, I can tell you with pretty good authority that any thing striking a rotary wing in flight can cause immense damage even a crash. Your right, that drone would not fly upward into the rotor wash. The most likely scenario for a main rotor collision would be a heli making a banking turn into the the path of the drone. A tail rotor strike would be less catastrophic but in low altitudes autorotation landing becomes more and more difficult. This whole conversation veered off in a different direction than how it started, but it is still one worth having. The fact is, that helicopters and drones are often flying in the same altitudes and a collision is in no ones interest. And the helicopter would always get the worst of it. Replacing a drone will cost couple thousand, replacing a single main rotor blade can cost 30K with installation and re-balancing. And in the event of a crash, you cant replace a life.