A man recited Surat al-Fatihah during the tashahhud, then realized his mistake and repeated the tashahhud; is the prostration for forgetfulness obligatory upon him?

The questioner : Similarly, here a man recited Surat al-Fatihah during the tashahhud, then realized it, meaning he remembered and immediately went to repeat the tashahhud; is the prostration for forgetfulness obligatory upon him?

The Shaykh : Yes

The questioner : What?

The Shaykh : Yes

The questioner : The prostration for forgetfulness is obligatory upon him. Similarly, if this person did not realize it and did not notice his situation until he had said the closing salam with the imam... and what is required of him here?

The Shaykh : May Allah forgive you, you inserted a phrase that changes the question and consequently the answer.

The questioner : Yes.

The Shaykh : I said "with the imam."

The questioner : The first one did not mention an imam to you.

The Shaykh : Yes, so now, with the imam, the prostration for forgetfulness is not obligatory upon him.

The questioner : Never.

The Shaykh : Never.

The questioner : Yes, but if he was alone, it is obligatory upon him.

The Shaykh : That is the previous answer which you did not ask about.

The questioner : Yes, yes, it is the same, but I said in the second part, if he did not realize it and became... what? He said the salam for himself, meaning, does he repeat the tashahhud a second time, or is it just the prostration for forgetfulness?

The Shaykh : Just the prostration for forgetfulness.