be lost to the world

To be fully and deeply engrossed in something, such as a thought or idea, often to such a degree as to be unaware of or insensitive to the one's surroundings. It's no use trying to talk to Helen when she's lost to the world like that—it's as if we don't even exist! I've been lost to the world all day because this TV show is just so good! Sorry, what did you say? I was lost to the world there for a minute.

be lost to the ˈworld

be giving all your attention to something so that you do not notice what is happening around you: When I went into his office he was staring out of the window, apparently lost to the world.