He does message Sage, just after you choose Jill he says, "Yeah, but I need to write a text before we leave.". Then your chat history shows, "Sorry, Sage. I can't make it right now. Something came up. Is it cool if I drop by later?" and if you're serious with Sage she messages back, "Ok... No, don't drop by. I changed my mind.", otherwise, if you're just friends she messages, "It's fine. I'll manage." Unfortunately you can't see any of these messages yet. You'll see them next episode when you get a chance to look at your phone (I don't think there's any opportunity to look at your phone messages from this point onward in e6).