When you activate a draw tool and start drawing on the map, if you suddenly right-click, the drawn graphic will remain on the map and it's like it is not even part of the map and there is no way to remove it. If you look at map.graphics after you do the right click, it's empty!
You may say well nobody is gonna right-click in the middle of a draw, but I have seen it happen many times especially on touch-screen devices where people touch the screen with their other finger in the middle of their drawing.