Within the last few pages of this thread, I believe there was a suggestion of looking at the delivery stops log for the truck. That might tell us if the truck went into Juchitan de Zaragoza before heading to Santa Maria Guienagati. If such a delivery log exists, it might be possible to see if anyone at those delivery sites saw Jenny. If they did, it would be possible to eliminate some of the route from where she was picked up (as far as trying to identify places where she could have been removed from the truck). A shot in the dark, I know, but not out of the realm of possibility.
Can you tell me exactly where Lagunas Crossing is on this map? Do you have a feel for the route that the truck took
I have the advantage of many trips to Mexico, and am quite sure the semi was only moving between the breweries/major supply depots. From the supply depot, small trucks make deliveries to all the stores/bars in towns and villages, where semis can't maneouver. Also there are 2 or 3 staff per delivery truck for security since the truck is open (driver, unloader, deliverer) so no room for passengers. The delivery trucks look like this http://tinyurl.com/h8rknp3
The semis, I think, are completely locked down and can't even be opened by the driver, to prevent robbery. So only 1 person is required in the truck.
On the right hand column of the log on p 68 at 7:14 pm it says "[ESPERANDA DESCARGA]", I believe this means 'waiting to unload' (its contents at a depot.) Here's an image when I search the phrase 'camion esperanda descarga' http://tinyurl.com/jrs5w57