C.G.
You can try doing things with him at home like peek-a-boo so that he gets used to not seeing you for a second, then knowing that you will reappear when he opens his eyes. Also try it with a small blanket or cloth over his eyes. Hide and seek could also help. At first, let him watch you hide behind a couch or door, then let him "find you." Then, let him hide and you find him. He needs to know that you are still there even though he cannot see you. Do this several times a week and make it fun.
Also, the other suggestions sound really helpful. However, I would not sneak out when he is not looking because then he will never know when you are about to leave and will awlays be anxious. If he knows that you will not leave unless you have given hugs and kisses, then he knows what to expect.
Good luck!