Glad you walked away from that one.
You do seem to have an awful lot of rear-end crashes in the USA.
They are so rare for motorcycles here in the UK/EU that I have never even heard of one.
The most common motorcycle crashes here are known as SMIDSYs (Sorry Mate I didn't See Ya), where the blind/distracted/incompetent car driver pulls out of a side turning.
Hopefully it's just the swingarm that's damaged, but if it was me I'd insist on getting the frame x-rayed before I bought it back as that kind of force may have cracked the rear of the frame.