: In ODST we looked for clues and, somehow, finding those "clues"
: gave us information about what happened to the team mate associated with
: that clue. The mechanics of this made no sense. The clues were artifacts
: and those artifacts couldn't give us the wealth of knowledge that we
: gained by finding them.

I'll disagree a little with that, if I may. I don't think it was ever suggested that the Rookie determined much from the bits and pieces he encountered. For instance, his finding the activation plate from one of the det charges within sight of the burning ONI building only told him that it was the UNSC blew up the bridge and may have also been responsible for destroying the ONI building. From there he simply moved on about the city. Now we, the player, got to relive the actual encounter with Mickey and Dutch at the bridge and ONI building, but I wouldn't suggest that the Rookie knew the details of that info as well.

The Rookie ultimately is reunited with the team underground and he's led there by the Superintendent who was privy to most of what went on with Buck and the squad whenever a portion of the cutscene involved a security or traffic camera.