I also don’t think it would get too lost either. Even when you watch the scene, I don’t think right away the audience think “Vader knows Luke is there” when he asks about the shuttle. It seems RIGHT at that moment the thinking was more like “there is a shuttle that came from no where and wants to go to planet, that seems a bit odd.” Hence, why he wants to know what that shuttle is doing. Once he begins focusing on the shuttle, then he sensed Luke’s presence.
Exactly. Then the dialog from Luke tells us that Vader knows he’s there. I mean, they actually say it out loud! It’s not a subtle moment.