Irish John/Steve.... Sue or at least investigate
Sorry to hear about your 'little incident',
I am impressed you managed to not have one for 47 years of riding, excellent work there, must have some good skills.
I would suggest maybe another lawyer if this one doesn't like to sue the state and you should probably get a copy of the incident reports from the LEO's and FD staff who responded.
If you were told to "go ahead and ride home", that is one thing, but if you were recorded as 'insisting you could ride home' (refusing treatment) that is something else. SOP's are not always followed but reports should indicate if not and why not. In a former life I was a paramedic and clearly someone failed to examine you sufficiently to discover your injuries, in my experience there's not too many reasons that can happen and you should definitely find out which one is recorded.
(That's not to say it happened that way but that is what got recorded!)
Either way there is no way you should have been permitted to leave the scene with those injuries.
Hopefully you also had the presence of mind to have someone take photo's of the accident scene showing the excess powder/spheres and skid marks while they were still visible? (you said you went back there, I figured that was why)
I am not suggesting you try to get rich off this, but if you can get your medical expenses covered that would probably help things out. The next rider might not be in a position to complain....
Either way, I hope you heal fast and heal well.
Keep riding as well as you always have, I hope your next accident will be another 47 years away!
Before anyone kicks me for suggesting this course of action...
I used to know a guy who had an accident and got sent on his way with a concussion.
He went home and felt like cr*p, took some aspirin and had a nap on the couch. He woke up bleeding from the nose and could not make it stop. He went to hospital later that night and died on the table from a ruptured blood vessel in his head.
Concussions can be deadly if not treated, one bad enough to affect the pupils is very serious.