Skull problem on Halo 3.?

[Osian]

I am trying to find all of the skulls on halo 3 to unlock some armour. I was checking how many I had collected and it showed 3 had been collected however I have definitely collected four. My friend played campaign with me through xbox live and picked up a skull that is one of the four. Does this mean I can't get the skull because my friend picked it up?

 

[Phillip]

I and my friends play Halo 3, when I pick up the skull, both of us get the achievements, so I guess we both get the skull, but you may ned to pick up the skull.

 

[yelixir]

U can go back and get it again but yeah u didnt get it because u need to pick it up yourself

this link might help you

http://www.haloforever.com/halo_3_skulls_locations.php#mythic