This is earned for finding optional collectible #3. If missed on the first run, you can "Play Episodes" and select specific parts of the Episode in order to find the missing optional photos through collectibles mode
. The following collectible is described and can be seen in the video below at 2:28:
As you walk along the road in the desert, you'll pass by a billboard, and then notice an animal on your right side. As you approach, it runs away. Follow it to its den, and spot a skull on the ground nearby.
Getting all 6 collectibles in this episode will also reward you with the following: