They didn't file with the rangers because it was only a day hike. But they should have left a trip plan with someone. Then when they didn't show up when they should have, that person could have sounded the alarm the night before. They still would have spent the night on the ridge but there would have been folks looking for them in the morning. They were damn lucky a random cyclist came by and heard them or they would have been dead by the next day with still no one even knowing they were missing.