This is earned for finding optional collectible #1. 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 1:00:
Found at the campsite, by petting the dog 3 total times. Between each interaction, they will move locations. At the end, they will dig up a collectible, and you can pick it up.
Getting all 6 collectibles in this episode will also reward you with the following: