My katana and security armor have disappeared from my appearance, I was playing matchmaking wearing security shoulders and katana back and in game it wasn’t showing my back or arms. After that game my katana and security helmet(but not the arms) were no longer in my appearance tab.
Closing as you’ve already posted in the relevant support thread
https://www.halowaypoint.com/en-us/forums/8f4648981f554a9d86527a5754966e89/topics/missing-armor-in-halo-3—recon-rogue-helmet/4282548f-9041-4b61-93b2-0b66d227cc65/posts