What happened just before you got it? What achievment was it before it dissapeared? Did you recover your gamertag someplace else? If you can answer these, I might be able to firgure it out.
I got them from getting a little more than 1000G in Halo. Then, I got the MVP achievement and they disappeared. All I have left is the Security shoulders, which I think you get from 900G in Halo. I never had to recover my account, either.
That is one of the weird glitchy armor pieces. They always have problems with those pieces, and they best way to get 'em back is to either send a letter to Bungie or earn more achievements. That sucks man, I hope you get 'em back...
I looked at your achievements and you don't have all the originals. The glitch is somewhat iffy. I still don't have the last 4 Campaign Meta-game achievements but I have 62 total for 1385 points. I think you either have to get the originals or just a majority of all the achievements because I still have my Katana. (I just got the zombies achievements but I haven't edited it into my custom sig)
Try and get one more old achievement. If that doesn't work, get all of the old achievements. That'll permanently fix the glitch, you just need to get that overkill and laser double kill now :/
Yeah it is a bit weird my katana first appeared when I reached 1000 but it stoped disappearing after I reached 1100 but it varies from person to person my friend got it at 800 and it never disappeared, I guess the only sure way (as said before) is to get the 49 originals.
OMFGWTFBBQ DO A BARREL ROLLLL IT THE END OF THE WORLD NOES WERE B MEH KATTANA ARMAH?!?!11 It's just armor. Doesn't make you better at all. But if you want just get every achievement (original) like SBJ had suggested. Sorry but after watching arby n the chief, there's an exact episode on this.
I can help I keep getting the same problem so heres what i want you to do... 1.Get An Achievment 2.You Katana should be back 3.next time it and your security go away change your helmet to E.O.D 4. After that your body should glitch and change back to katana make sure you only change it to eod no anything else or you will have to get another achievment **if you want it to stop going away get all the original achievments