During the scene where Harry battles Draco in the bathroom, Harry sends a spell down a hallway, striking Draco and sending him to the right, out of sight. As Harry moves forward from the hall into the room Draco is seen on the floor bleeding. At this point Snape appears behind Harry moving from Harry's left to right. Just as Snape clears Harry, if you look between Snape and Harry, down the hallway behind them, you will see what appears to be Draco, even though at that time he should be lying on the floor in front of them.