What is the ruling on the congregants who did not complete the rak'ah after the imam's prostration of forgetfulness, and then left the mosque?

The Maliki school and the majority of scholars hold that if someone lags behind the Imam by two pillars due to an excuse, they should catch up with the Imam and perform what they missed. Otherwise, that particular rak'ah is invalidated, and it becomes obligatory to complete a replacement rak'ah after the Imam's salutation. Therefore, whoever fails to perform the missed rak'ah must repeat the prayer.