Halo 3 IWHBYD Skull doesn't make the helmet appear, HELP!?

[British China Dude]

Ok, So 1st things 1st. I finally got the IWHBYD(I would have been your daddy) skull and I checked that I actually have it and I do. And I got all excited bout my new helmet but when I check in my armor section, It's not there!!! And yes I did check in the helmet section. This is what I did, Played through the level one day, Then got up to the truth section bit. Got irritated because I wasn't getting skull. Saved and quit. Next day continued trying, after the 3rd attempt I finally got all those rings to light up and I got the skull at bridge. And that's when this happens which is why I'm asking you this right now...

 

[BURNT FISH]

I thought it only unlocked hidden dialogue... (which makes chars. say funny stuff)

 

[Lisa]

I believe you have to get all gold skulls, or silver skulls.

 

[the black guy]

you have to do the whole last level from the beging hope ive helped