Are there circumstances that could make the starter go out...like going through creeks and getting water in the engine area? Are there things that going through creeks would cause that could make an issue look like it was a starter issue, when maybe it is just a water in certain parts that are the real issue?
From looking at overhead pictures of the Horman house, it's clear they live on a gravel road.
In my part of the country, at this end of winter, the gravel roads are all in bad shape. Washboard sections, potholes, mudholes, I can find all of that within a half mile of my house.
I've seen frequent references to wet, rainy weather in the week before Kyron disappeared. In fact, the search was hampered in the first couple days by rain.
If the starter went out due to a water splash, who is to say it wasn't due to the driver hitting a pothole full of water? Or splashing through a mudhole in a low section of road?
Personally, I think the truck would be of extremely low evidentiary value unless it had an unusual quantity of human blood found in it. It was the family truck, it's only to be expected that evidence of Kyron would be all over it.
Now, if someone associated with the school but with no known history of having Kyron in their vehicle turns up to have Kyron DNA in it, that would be of high evidentiary value. Kyron's DNA would have no business being in such a person's vehicle.
But in his own family's vehicle? Every reason to find it there.