Yes, the North American 335d M-Sport was only available for the 2011 Model year, which was the last model year the 335d was produced by BMW. The 2011 Model year began production early in 2010. (Mine was a March 2010 build)
I have only seen 1 M-Sport in my travels out of the about a half dozen 335d's I've seen. The M-Sports are out there though hard to find.
I have one also.