What would happen if a helicopters rotor hit the [in-air] refueling probe?
It would chop it right off.

Watch the video. It's fun. When the helicopter pitches up right after refueling, the rotor disc cannot follow the movement (its hinges allow the blades to pitch up and down, and inertia makes it change its plane of rotation only slowly). The refueling probe is cut cleanly in half.

However, I would not try this on purpose. The risk of damaging a blade is considerable. I am sure the rotor blades needed to be replaced after that incident.