I thought I heard someone trapped in a tree, once.
I walked all the way up to it and tapped it on the trunk. Nothing happened. Pressing my ear to the bark, I tried to focus in on the noise that I had heard. There was nothing. The gentle sighing, masking a greater anguish, had gone.
Nevertheless, I climbed the tree, all the way to the top. I hung from the thinnest of branches and tried to find that noise.
Eventually, the branch snapped and I was quickly reconnected with the ground.
I never found that person trapped in there.