There's a difference between a collision and liability claim when it comes to rocks and the insurance companies. If a rock falls off a truck and hits your car before it hits the ground, its a liability claim and the trucking company usually covers it or you only have to pay your liability deductible.
If the rock falls off the truck and hits the ground/roadway first, then its a collision claim, and generally not covered by their insurance and you have to pay your collision deductible.
If the rock falls off the truck and hits the ground/roadway first, then its a collision claim, and generally not covered by their insurance and you have to pay your collision deductible.