What you saw was the sterile draping we use during surgery it is a large often blue canvas that is sterile and blocks off surrounding unsterile areas from the operating field. You do see it on TV as well. The anesthesiologist, who is not sterile, sits on the other side of the draping, near your head. The draping also helps prevent bodily fluids from spraying onto the anesthesiologist and your face.
The drapery has nothing to do with preventing you from seeing the surgeon’s activity.