This narration says that the Prophet(pbuh) forgot a verse but another person remembered it. We can easily understand the standard of Prophethood among those fellows who announce that all the narrations of Bukhari and Muslim are true. This is an insult of Prophet Mohammad who is the head of all the Prophets. The verses of Quran were revealed on Prophet Mohammad but he forgot and a common person remembered it.

Actually such theory of Prophethood is against 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".

http://sunnah.com/muslim/6/265