Your camp should be found by the renegades around day 10-12, automatically triggering the "Spotted!" event and achievement. During this event, make sure to chase after the renegade with a healthy survivor from your camp. You should catch the renegade and unlock this achievement.
Be aware that the survivor you use to chase down the renegade has a high chance of being badly injured and will need to be treated at the quarantine point.
See the video below for more information.