The car was red, not blue.
I went home, not to the supermarket.
In these two examples, which use the word 'not' to create contrast, are we seeing a case of ellipsis? Could we find the original forms of these sentences by adding the missing components that would make it grammatical? (See below.)
The car was red, and it was not blue.
I went home, and I did not go to the supermarket.
I think that this explains what is happening here, as the extra words are superfluous.