I just finished a run through of 1.21 and after the guy saves you its on the ground outside the cell for me. The only other place I know if I am remembering correctly is in the base behind the magic force field off the lake area near where you save Shany. But you have to go through several Yslide to get to it in a chest. And it should be the last area you visit to end the game. So it will be the tuffest area yet for you.
Try loading a previous save and getting to the dungeon again. The armor should be there after you are saved and talk to the guy. Hope this helps!