No, I think Smackie is right. When my friends and I first hit legal drinking age, we went out to the bars a lot. If one of us hit it off with a woman, he was going to pretty much ignore us friends while he was creeping on her. Sometimes one of us would just disappear because he got lucky and was going home with some woman. It was unsettling at first, and seemed really rude, but getting laid is really important to a young guy, so friends need to be patient and tolerant. One time, we sent one of our friends to pick up fast food while we were watching a football game. McDonald's was only a half-mile away, but he was gone for more than three hours and came back with cold food. Why? He talked a McD's counter girl into going out for coffee with him after she got off work. We were annoyed, but it was also kind of funny and desperate, too.
It's slightly possible that your friend is some kind of special case, with some sort of weird mental or physical problem causing these disappearances. Or maybe he is a masked crimefighter and will never be able to explain his disappearances to his friends. But trust in Occam's Razor... he is probably just putting pursuit of the ladies ahead of his friends. That said, it also means that your friend is a self-centered tool, and you might be happier dropping this friendship.
Good decisions come from experience. Experience comes from bad decisions.