This narration says that The Holy Prophet forgot a verse but another person remembered it. We can easily understand the standared of Prophethood among those fellows who announce that all the narartions of Bukhari and Muslim are true. This an insult of Prophet Mohammad (pbuh) who is the head of all the Prophets. The verses of Quran were revealed on Prophet Mohammad pbuh but He forgot and a common person remembered it.
Actually such theory of Prophethood is aganist the verses of The Quran. PLease read the verses of Quran (75 : 16-17) ” Move not your tongue with it, [O Muhammad], to hasten with recitation of the Qur’an. Indeed, upon Us is its collection [in your heart] and [to make possible] its recitation”.