You need to look at the insurance laws in your state to know how to proceed. If you are in a no-fault state, it could get dicey. If you are in a traditional state, and the driver of the car has insurance (not a given around my area, with all the illegals on the road), you may be in need of an attorney to fight with that persons insurance company if you expect book retail or better. Most insurance companies will try their best to lowball you. And if the other party was definitely at fault and there is a police report stating that, you may have no recourse at all against the dealership. After all, you took the bike to them to diagnose and fix a problem, and a test ride is part of that process. If the tech wasn't negligent and was just a victim of another driver's illegal action, I'm not sure what you can legally expect of the dealership.
In other words, it isn't just a simple answer. You need to protect your interests, and don't sign anything until you do all your homework.
Jerry