I think when he says "you're leaving me in lieu of this song" he means that she's leaving him instead of telling him that she has a problem, instead of trying to work things out. Because the song is called "Rough Draft" && it's about how he writes her a "rough draft" of how he feels, hoping she'l read it and try to fix things and he'll "reappear". But she's leaving him without making any effort like that.
It makes sense when he says "so is your blank stare in lieu of this song", like instead of telling him how she feels, she's just giving him blank stares.
I think when he says "you're leaving me in lieu of this song" he means that she's leaving him instead of telling him that she has a problem, instead of trying to work things out. Because the song is called "Rough Draft" && it's about how he writes her a "rough draft" of how he feels, hoping she'l read it and try to fix things and he'll "reappear". But she's leaving him without making any effort like that. It makes sense when he says "so is your blank stare in lieu of this song", like instead of telling him how she feels, she's just giving him blank stares.