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 4:13:
Upon moving the water jugs at the campsite, you will meet up with Daniel at the lake. After the conversation, scan the right side of the area to find a fossil sitting behind a log.
Getting all 6 collectibles in this episode will also reward you with the following:
https://www.trueachievements.com/a260746/lost-boys-chronicle...