[ineedtosleep]

I would take a guess that it is type of Ellipsis[1] -- more specifically, Answer ellipsis[2].

[1] https://en.wikipedia.org/wiki/Ellipsis_%28linguistics%29

[2] https://en.wikipedia.org/wiki/Answer_ellipsis

EDIT: Keep in mind, I was writing this response before links to the Atlantic were posted (which I haven't read yet).