What is the ruling on someone who forgot to say "Our Lord, and to You be the praise" and did not perform the prostration of forgetfulness (sujud al-sahw)?

If someone forgets to say "Rabbana wa lakal-hamd" (O our Lord, and to You be all praise) after rising from bowing:

If he is a follower (ma'mum), he does not have to perform the prostration of forgetfulness (sujud al-sahw), and the Imam bears it on his behalf.

If he is praying alone or is an Imam and forgets this, his prayer is valid, and he does not owe anything.