What is the ruling for a follower who forgets a pillar of the prayer behind the imam?

The Shaykh : Now it is your turn.

The questioner : If a follower forgets to prostrate and only performs one prostration due to some circumstance, does he perform one rak'ah after the imam's taslim, or does he only perform the prostration?

The Shaykh : It depends on the prostration he missed. If it was in the last rak'ah, he performs it and completes the prayer. If it was in a rak'ah before that, he performs the rak'ah.

The questioner : And if he forgets to recite al-Fatihah in a place where it is obligatory to recite it behind the imam?

The Shaykh : The same answer applies.