Same thing happened here , gravel from a truck hit my windshield at 65 mph. I caught up to the truck and got his license plate number, company name etc.
Called the company and my own insurance .
Too make a long story short , was told that unless the truck owner admits his truck was the truck that the gravel came off of and hit my windshield I was S.O.L.
Of course he would not admit to it. I asked the trucking co. if a driver has ever admitted to gravel falling off of there truck and hitting another car , there answer was not in the 20 year history of the company has a driver ever fessed up.