Is the prayer incumbent upon the ignorant congregant who was unable to alert the Imam to his oversight?

A Muslim must learn the rulings of individual obligations (fard al-ayn) such as prayer and fasting. Knowledge of the Shariah rulings related to what Allah has enjoined or forbidden is an obligation for compliance or avoidance. Accordingly, both the Imam and the congregant must learn the rulings concerning the validity of prayer and its related matters, such as the rulings of prostration of forgetfulness (sujud al-sahw). Ignorance is not an excuse for neglecting to learn them.