It depends on how far the arrow penetrated . . . and at what angle. If you hit the ridge along the scapula and didn't get good penetration, he might be alright. Also, if the angle was steep enough, you might have missed the other lung. I've seen deer live with one lung. A friend shot a 6 point years ago and lost him figuring he was dead somewhere on the farm. Two months later - during gun season - he was shot by a shotgun hunter. They found the front 6" of his arrow just under the skin . . . healed over. He might make it.