Q. The imaam made sajda sahw. I stood up when he mae the salam. I did not make the sajdah sawh. Could I have made it in the end? Does the sajdah sawh apply to me for a mistake I did not make?

A. The Imaams sajdah sahw becomes binding on all those that are behind him. Since you did not do as you were commanded to do by the Imaam, you have voided your Salaah. Thus, repeat that given salaah again.

In future, wait for the Imaam to make a complete tasleem (salam to the right and left) before reading rakats you have missed.

Allah Certainly Knows Best.