Seriously, what planet do you come from where driving into the back of stationary vehicles is ok?
I think that’s kind of neither here nor there, unless the driver braked in an unsafe manner (ie, emergency stopped when there was no emergency) – he stopped somewhere he shouldn’t have, the cyclist who rode into the back of him maybe had some observation issues.
The problem, I think, is that legally the driver had a responsibility to have given him his details. Morally, laughing at him and saying “you’ll never find me” is also not very nice.