The Dennis Martin case

Dennis Martin was a 6 year old boy who mysteriously disappeared in 1969 in the Great Smoky Mountains National Park. He was playing with his brothers and another family, while under the supervision of all the parents at all times

The children were playing hide and seek, and the parents saw Dennis hide behind a tree. When he was not found by the seeker, they went to look, and he was no longer there.

Because of the landscape around said tree, it should have been easy for the parents to see him if he had run off. The Appalachian trail (Which is known to be a trail many people disappear on) was nearby, and his father immediately set off along it, looking for him. When he had no luck they called the park rangers and searched for him all night.

The search for Dennis became huge and lasted almost 6 weeks. The FBI, Green Berets, Rangers, and local volunteers turned out to look for him

Despite all this, all that was ever found of Dennis was one shoe, and one sock. No other signs were found.