What is the ruling on someone who forgot a circuit of Sa'i between Safa and Marwah during Umrah, then exited ihram and remembered afterwards, so he went to complete it?

If someone forgot a circuit of the Sa'y of 'Umrah or part of it, their Sa'y is not complete. They must return to their state of ihram, avoid its prohibitions, then complete what they missed of the Sa'y, building upon what they had already performed. However, the majority of scholars prefer that they repeat the Sa'y from the beginning. After completing the Sa'y, they should shave or shorten their hair. Their previous shaving or shortening is not counted. There is no fidyah upon them for doing this out of forgetfulness, and their 'Umrah is valid.