OK, the guy's description was a little confusing, at least to me. In trying to see it in my head, the minivan cut in front of him and took his lane? Or, it also sounded like the minivan was just passing through his lane on their way to another lane?
In any case, he did say he was riding much slower than the posted limit.
Here in MI, even if the twatwaffle in the SUV was putting on makeup whilst texting on her phone as she barreled in front of you and slammed on her brakes in order to turn into the McDonalds, you still generally get the ticket for following too close. Sucks, but that's the way it is.
And as for info, last accident I was in (many moons ago, knock on wood) I got the witness name and phone numbers myself. If they wanted to stick around long enough to talk to the police, even better, but at least I had names and numbers of those folks that had seen what happened.
And quite possibly, if the guy hadn't argued with the cop when he stood back up but clearly explained that he was having some physical issues with his knee, and even went so far as to ask the cop where he could safely stand, he wouldn't have ended up on the potential badge-induced jump-start list.