Not sure how a broken lock washer and nut end up in the same spot? The nut would have to rotate to the point it released from the ball shaft and should not fall at same point unless glued together. Most of the time when I have tried to remove the nut, the shaft of the ball is peened by rocks to make it very hard to remove.
I would think the most important statement is grease your ball. Without traction/grip no turn of the ball, therefore no failure.