In a comment John Lawler wrote:

Note that the responder doesn't say the participle (had noticed) required with a perfect auxiliary have. The questioner uses the auxiliary for an infinitive (didn't notice), not a participle. Consequently, if you filled in all the missing words, it isn't ungrammatical, just not parallel: Perhaps you didn't notice [it]. I can't say I have noticed it. This violates the attempt at reduction, but is clear enough. And this is a movie, not real speech.