No good news yet.
This article brings up an unfortunate fact:
The family has remained in seclusion, but through Evenson said the boy suffered from a form of autism known as sensory integration disorder, which causes him to cover his ears and hide when he hears loud noises. Because of his condition, searchers have been asked not to blow whistles or sirens.
Don't know if this applies to noises he makes himself, but might explain why a whistle wasn't part of the picture, and seriously handicaps the searchers.