Ya know SWC ...
what your son is doing (leaving home ... not coming home and not calling to tell you where he is) is incredibly inconsiderate. He is using your family home as a he would a hotel ... well except in a hotel he would be required to pay for his keep.
It is civil behavior to let those you live with know where you are and when/if you'll be home.
Have you considered how he is taking advantage of you and your good graces??