Missing Martial Arts Outfit and Category

Take them to CAS while they are supposed to be wearing the outfit, but isn't. Do this through MC, not the dresser, by clicking on your sim. Its there you can change their outfit. It's been a while since I did this, but I was able to fix their outfit that way.

ok, well, I did fix it but thought I would post here how I did it in case it ever happens again and anyone else that might need to know how to do it.

Have the sim practice martial arts - find a different sim and use Master Controller to -gift' them a level 10 martial arts status - go to Intermediate settings on this other sim and click on 'transfer clothing- - choose active family and then select the items you want to transfer (Martial Arts 1 through 9) - then click your sim and choose Nraas>Basic>Outfit and choose the outfit you want - the martial arts category should now appear for your sim as well as if you click them or a dresser and change the outfit in game.

Don't know why it dropped the category but thankfully I got it back - and some random sim just become a martial arts expert overnight!