Regrets, sorry you encountered this and wish you a speedy and full recovery.
We're you "cited" as a result of the accident? If yes, please tell us.
Collision avoidance is all part of SEE (see, evaluate, execute) as taught us (or those of us who partake) in the MSF Rider Training courses (always the right thing to do

) that not only are swerving techniques essential, but keeping a safe speed and distance between ourselves and those in front/rear of us is critical.
I hear ya - that sudden, fast stops may and will happen....I am also sure you'll avoid this situation in the future and keep a safe'r distance.
Similarly, on our ride back from the 69th Sturgis Rally last month heading south toward Denver, we witnessed three fellow riders (2 males/1female) who took it upon themselves, to skirt off to the emergency lane in their haste to ride ahead of congested and slowed traffic (due to an accident up ahead), only for us up ahead to find the front rider - scored off the road itself and down due to a passenger vehicle which did the same (as you encountered), by pulling off the traffice lane and over to the shoulder/emergency lane without looking back.
In this case, it appeared to us that like you, the front rider could not avoid it and was side-struck, rolled his scoot and himself down into the ditch while his fellow riders behind him had likewise both dropped their bikes. Luckily for them all 3 riders seemed to have received no serious injuries. (we did all stop to help them, checked that they were ok, pick up their scoots for them and wished them welll before we proceeded to get back on the road, in the traffic lane and underway).
Without a doubt, I am sure the front rider (and likely the 2 with him) receieved citations for improper lane use as a result of the accident once the police arrived.