This is a really good interview with the sheriff where he recaps exactly how Christopher went missing and what the mother and grandmother have been doing. I’m going to transcribe it and add it to this post here in just a minute but I wanted to post it now.
It sounds to me like he was last seen in the road right before the road turned.
ETA:
Reporter: Forgive me but it is my first day covering this story so please forgive me. How did this boy get out of his mother's eyesight?
Sheriff: Ok, ah, a little recon on that. They returned. She and her mother returned from a venture they do every day at
two locations around this area where they
sell food out of two big coolers, ice coolers. On the
side of the road in Plantersville, Magnolia area and they do that
every morning so they were returning unloading the coolers at their house. The boy was outside playing with the dog, just a moment or two while they were going inside, came out. The neighbor saw him
running down the road. Saw their dog, they called the mother, they ran out that way. Maybe if you visualize the football field, the 60-yard line is where they last saw him. The
road turns right to the south and that's the last they saw him. The dog came back so that gives you what we are dealing with now.
Also earlier in the convo Sheriff was asked if Christopher had siblings and he said yes, older maybe 10 years old or so.
The only ones here at the time of disappearance was sibling and mother and grandmother.
Wildlife - deer, rabbit, coyotes, snakes, wolves.