Hadhf does not necessarily make a sentence defective. When a contextual clue identifies what is absent, the meaning survives; at times omission makes speech more effective, concise, or tactful.
Example: Question: “Who came?” Answer: “Zayd.” The full sense is “Zayd came.” The verb is unspoken because the question supplies it.
A sound analysis identifies (1) the omitted element, (2) the evidence for recovering it, and (3) the particular rhetorical benefit of leaving it unspoken.