If the user that posted the question deletes the code to which the question belongs to, after accepting an answer, should one restore the code or simply notify the user or moderator?
If the user has decided they don't want the code listed on the site, I think we need to delete the question. Asking for code review on code you don't want people to see is well silly, but it happens somehow. In this case, the user asked for the question to be removed so I did. I think we have to respect the poster's desire not show their code.
So: You should flag questions which have code removed, and the mods should delete them.
Deleting code from a question after it received answers is certainly not acceptable behavior. If the code in question was sensitive or something like that, the poster can delete the whole question.
Code Review is different from other SE sites in that pretty much every “question” here is “too localized”: it's not likely that someone else will have exactly the same question. But that doesn't mean we should make our answered questions even less useful for others.
I think restoring the code is the right way to go here, so I did just that. If something like that happens in the future again, feel free to restore the code yourself. And since you don't have the reputation required for non-reviewed editing, your edit will be reviewed by someone else anyway.