Found a crop circle and heard a mysterious voice.

Missable.

After the Laughing Octopus fight in Act 2, you will have to track Naomi's footprints. As you are doing so, you will come across a river (make sure not to mistake this with the first river you cross, over a bridge) which you run directly through. Instead of crossing it, look to the left where you will see a set of a footprints. Follow those footprints and you will find yourself in a crop circle (basically looks like circular-shaped grass). Once there, an audio flashback will begin of Roy Campbell, which when finished will reward you with the trophy.