If the island has been mapped with lidar, it would be possible to find it in such way. Lidar can penetrate the trees and give you a surface model of what underneath.
You should be careful with the "can penetrate the trees" statement for people who don't understand the technology. But you are correct. Like light, some of the lidar can make it to the ground and give us a partial map of the floor.
I'm sure more passes from different angles would get a better picture as well.