Lost and Found Contour

When only some contours are visible in a work, it's called a lost and found contour.

In this Caravaggio painting, "David with the Head of Goliath" he has used this technique. You can see that parts of David's body isn't seen because it is in the darkness. This does not mean that his shoulder is missing. It is just implied.

This is very useful in creating emphasis, as you can see in this other Caravaggio piece.