No he did not appear at the cleansing. Of course, Cyndane might have noticed that she was channeling at her own mindtrap. Or rather, she would have been on the ground writhing in pain from the attempt.

Otherwise, Moridin would have had to give the mindtraps to someone (because he, or someone, stroked them during the battle), which raises the question of who he would trust for this.


But the real reason this is impossible is because he would have just Travelled away and left a great big hole in Cadsuane's defences. Alivia was by herself for the whole battle, and Moridin desperately wanted the Cleansing stopped. Clearly they can't be the same person.