There had been some whispers that the location on the Terminals in the Halo Anniversary edition of the game would move dependant on the degree of difficulty the game was set at.
Frankie (the dude who draws Mister Chief) left a note on the interwebs to clarify:
"This used to be true, but was changed during test. Now they are all found in the same location, regardless of difficulty. In part so that players can switch difficulty in saved games, but there were other, more tedious reasons. The first one is very simple to find. They get progressively harder, however."
So there you have it.