Your H tells you that he just needs to be able to "vanish." He also said you could vanish, too.
If he tells you who he is with, and gives you more notice, say tells you before he goes that he's spending the night or calls you earlier in the evening, would you be okay with it?
Why was he afraid to tell you who he was going out with? Because that is obviously why he lied, to protect himself from some fear of what your reaction would be.
Did you know? Could you have said, "are you going out with xxx?" And if he said yes, are you comfortable with saying "do you think you will spend the night?" And then be able to say, that's great, have a great time, enjoy yourself, I'll miss you?
Would you object to him sleeping over with his friends if he were out on a hunting or camping trip? Somewhere remote where chances are he might not be reachable either?
You read Wild at Heart. You know he needs to be a warrior with his friends.
He is trying to be honest with you. Like Betsey said, he could always be dishonest, but he is trying not to be.
Maybe, when he goes out, you should go out... stayover with girlfriends? Just a thought.
Relax. Appreciate. Be calm. Laugh. Enjoy. Be secure. Be loving. Be loved. Don't personalize. Don't ASSume. Accept. Be grateful.