This sounds like a flat rear tire to me. I've experienced high speed wobble and as Neal said it doesn't occur at 55mph. When your rear tire goes down the bike wobbles from side to side until you either dump it on purpose or get tossed off when it goes into a barrel roll. Sometimes in the aftermath of a motorcycle accident when the rider doesn't understand what happend, it is hard to figure out the real cause. When a motorcycle goes down and skids along the pavement it more often than not chews up the rear tire enough that it's hard to determine if the accident caused the flat or the flat caused the accident. I caution all to continously check your rear tires. I often read posts about folks bragging how many miles they got out of a rear tire. I'm not pointing to Bobby's friend on this, just using what may have happened here to point out how cheap a good tire really is in the grand scheme. Trying to get more than 10k out of rear tire is dumb in my opinion.
Bobby,I am very sorry to hear about your friend. I hope he can move on with his life and adjust. I have known a couple of people who became paraplegic from motorcycle accidents. One all but quadrplegic. Somehow they found the strength to go forward and live their lives. One thing I believe in my heart is that your friend needs you, but doesn't need you to feel sorry for him for very long. He will need you to learn to adjust to his new life just as he will have to learn. Be his friend and go forward with him.
B B