I don't have a friend out there that wouldn't cover for me just as I would do the same for them. If you think he's not a good enough friend then keep him out of it all together. As a cover story, I like the idea of the gambling thing. It doesn't involve him and if someone does pin his ears to the wall he wasn't there anyway so he would have nothing to contribute to any conversation. If not that, then the idea of not even calling him at all would suffice although, but would there be a chance of it coming up some day in the future? I go back to the gambling story I'd even go as afar as tell your friend that the story is that it was not a "wild night out" but it was a late boring night with a few drinks at a sports bar or something like that. This way there's not much to bring up like: 'What did you guys do?.... 'Where did you go?' If it's a boring story there's really not a lot to talk about and it will pass in time. If your friend doesn't want to go along with it then I guess he's really not a friend.