I can't recall that model of knight ever being available to chaos. Some rumors said anyone could take it, but nothing official, so it's not like GW pulled a fast one on you. This seems like a lot of hilarious whining. And Gir's point is a pretty fair summation of Daboarder's. It makes no sense to be upset you didn't gain access to a model from a different army. A model your army never had access to through history.