You are spending all kinds of effort imagining what's going on in his mind. You don't know. Ultimately, you don't need to know. If he wants to be less close to you than he was in the past, then you two will be less close. He's got this connection with this girl and she has kind of replaced you. That hurts, but things like that happen. You grieve and you move on.

Running in to them together may cause you some pain, but there has got to be a limit to how far you go to plan your daily travels to avoid them. It doesn't sound like you think they are all worried about running into you. There is room in the world for all three of you.

Your question was, "Do I stay quiet?" Were you thinking of doing something different than staying quiet?" What are your options?