Interesting Brazilian Jiu Jitsu Technique

Well I was rolling last night and had a very interesting technique used on me. I wouldn't call it a good technique as it required much strength and speed. It is a very effective technique though against a lighter weight opponent or if you have a lot of strength I would assume it could be used on a heavier opponent. Basically what happened is I was sparring with a blue belt and he managed to get side control and then he moved to the north south position over the top of me. He grabbed my belt and began pulling it up toward my chest he continued to do this til it wouldn't go up any higher. He then proceeded to to jump up to his feet and lifted me up by my belt with him. He then took my back and fell to the ground and proceeded to work a collar choke. He pulled the technique off very quickly and I didnt see it coming at all as I was mainly concerning myself with trying to get to the turtle position without giving anything to him in the process. I hope this makes sense to those of you who train. If not drop a comment and I will do my best to explain further.