This is one of the Achievements that add points to your rank. Scavenger is earned by finding items using the Scan button on the map screen.
Requirements
Bronze
Aquire 20 items. Award 1 point.
Silver
Aquire 40 items. Award 4 points.
Gold
Aquire 200 items. Award 9 points.
Platinum
Aquire 400 items. Award 16 points.
Diamond
Aquire 200 items.. award 25 points.