This achievement is for Halo 3: ODST specifically.
Some players have reported this achievement to be very particular. If you do not collect all the audio logs in order, the achievement does not unlock.
We recommend making sure you collect each one in order as you go. You will see the list of the ones you got in-game.
If you missed one, you will want to re-play the campaign on co-op and collect all the audio logs again, being sure to grab the one you missed before and this should trigger the achievement toast.