You have to get the lidar down to the scan range, which they do with drones. The effective scan range of that particular lidar model is 1.5 to 15 meters. Compare that to 1000+m for aerial lidar. That means that they had to get the scanners to extremely low depths and were using very expensive drones, and the process was still extremely slow. They still had to target the search area using probabilistic models based off of available historical records, as a general search would have been way too expensive.