Very sorry to hear this Nixy but as you say, at least he's ok. As has already been said, I think he will be on a very flimsy argument if he attempts to apportion blame on someone else without witnesses.
Much much bumpier gonna fiddle around with damper settings one day next week & maybe adjust the stiffness of the sway bar to see how much difference there is
You'll need to stay away from those cattle grids for now