Is it true that the Prophet's wife (peace be upon him) did not wear the hijab over her head?

What is mentioned in the question is an outright lie, for Allah the Almighty said regarding the wives of the Prophet (peace be upon him): "And when you ask them [His wives] for anything, ask them from behind a screen. That is purer for your hearts and their hearts." Then He made an exception for their mahrams (unmarriageable kin) by saying: "There is no blame upon them concerning their fathers, or their sons, or their brothers, or their brothers' sons, or their sisters' sons, or their [Muslim] women, or those whom their right hands possess. And fear Allah. Indeed, Allah is ever, over all things, a Witness." And clearer than that is His saying, the Almighty: "O Prophet, tell your wives and your daughters and the women of the believers to bring down over themselves [part] of their outer garments. That is more suitable that they will be known and not be abused. And ever is Allah Forgiving and Merciful."