"...the father of one of the boys found them dead in the trunk of an inoperable car sitting just feet from where they had been playing."
Surely everyone (including the police) were within a few feet of this car...especially during the start of the searching. Were these kids not kicking and screaming inside the trunk, off and on, for at least two or three hours? I would think the average 3-4 year old (and these kids were a little older, weren't they?) would be making a heck of a racket to get out!
The police were not called until 3 hours after the boys went missing.
They might have passed out but still been alive.