In one episode of Seinfeld, Jerry is sitting there on a plane and the plane is running. He looks out of the window and sees Kramer is running after the plane. But in a second Kramer is out of sight. Jerry sits straight and says to himself, "Couldn't be."
My question is, why doesn't he say "can't be" instead?
Let me begin by saying that I've never watched Seinfeld.
"Can't be" would have made sense if Kramer was still in sight when Jerry made the statement to himself. Compare:
You have asked about truncated, elliptical sentences. If we were use a complete sentence, the one that I would use is this:
- That couldn't have been him/he.