Here is my opinion of the whole story that day, that appears to dot all the I's and cross all the T's, regarding the evidence that was not easily found on the internet.
Terri was apparently a known criminal by the Roseburg police department. Terri served as a substitute teacher at the school, so she knew how the teachers reacted when children were missing, and how to scam the emergency system by sewing confusion on the day before, by telling the school that Kyron had a (suspicious) all day doctors appointment on Friday. But the Doctor's appointment could apparently never be found. The reason why Terri did not personally kill Kyron is because although she may be a cold hearted sociopath, she is not so cold as to be able to personally kill him in cold blood and not be personally affected by it enough to not show guilt. She wanted to have deniability of both killing Kyron and knowing where he is, so she could beat a lie detector test (but she failed them), among other things. If one were to pick one point in that day, where Teri at least briefly showed some sign of a significant change in demeanor, it would be just after she had disappeared for 1 1/2 hours and showed up at her fitness shop at 11:40 AM, with an allegedly sick child in tow. Prior to that point in time, she initially was consumed with rushing to a Fred Meyer checkout to get a time stamped receipt as an alibi but failed to allow enough time to actually perform a thorough search for the cold medicine that she was seeking. A little later, Teri was still consumed with adding to her alibi by proving how much she loved Kyron to an almost perfect stranger by showing Kyron's picture taken that morning, to her fitness shop employee that she barely knew. She was not shocked at this point in time. However, this effort to provide alibi's for that morning, proved that she knew that something had happened to Kyron that morning. The 1 1/2 hours of missing time started after the second alibi effort in the parking lot, during which she somehow could not remember exactly where she was driving the white truck. After the 1 1/2 hours of missing time, she showed up at her fitness shop where the desk attendants had described her to the effect as "out of it", as if she had only recently been emotionally shocked. So during the 1 1/2 hours of missing time, she became emotionally shocked in some manner. Since it is not likely that she was hauling a dead Kryon around in the back of Kaine's anonymous white truck all morning without being shocked, she therefore was not hauling a dead Kyron around in the truck, or at all. Additional facts are that Kyron was last seen exiting the SE exit of the school with a strange man who had asked to use Kyron to help him bring in a child's display, when all displays had already been brought in. Also, Kyron had only then been recently asked by someone that he trusted (Terri) to wait near that SE exit so that he could get a ride to an all day doctors appointment (that Terri had just told him about, but could never be traced to any doctor)with a stranger. Between when Teri told Kyron about the appointment (that she had somehow forgot to tell him about up to that point in time) and when Kyron appeared at the SE exit, Kyron left a breadcrumb by telling his friend that he had an all day Doctor's appointment. Since Kyron had extremely poor vision, meeting a stranger was problematic, so he had been instructed by someone that he trusted (Teri) to wait inside for the stranger to come inside and escort him outside. That duel purpose strategy here also introduced a third party to the mystery to take the heat off of Teri, who then was last seen escorting Kyron outside, that law enforcement could later blame as the abductor. Putting all of this together, then during that 1 1/2 hours of missing time, Terri had met up with that stranger by driving Kaine's anonymous white truck instead of her rare red mustang that would stand out, and viewed a digital photograph of a dead Kyron that shocked her, whereupon she paid that stranger money for completion of the job that she had hired him for, using the $20 bills that she had been siphoning from the families ATM account. (Kaine complained that she went through money like water.) Since she would not want to have a policeman pull up at the meeting place, and ask if everything was OK, with a dead body in the stranger's trunk, Terri had to be viewing a digital photograph on a camera that was not a phone, of a very dead Kyron with probably a plastic bag taped over his head, and not an alive Kyron that was simply being constrained for abduction. Which then caused her to go into emotional shock, until her workout at the club restored her body to conditions that were not so incriminating and got the blood flow returning to her face. Also by focusing on weight lifting, she could more easily forget that what had shocked her, had ever happened, and that she could then say with a straight face that she did not (directly) kill Kyron and had no idea (exactly) where he was. Although arranging for his death is equivalent to killing him in any court of law. That is how Terri can live today, by denying that she killed Kyron and having no idea where he is, when she goes onto TV shows in order to try to convince the public of her innocence. Terri was never asked on TV, whether she hired somebody to either abduct or kill Kyron, nor whether she knew approximately where his body was disposed of. The most likely place where Kyron's body was left was weighted down in the river between Sauvies Island and St. Helens. Sauvies Island was picked as a meetup point because the Police have no reason to cross that bridge and look at farmland. Kyron's body slowly decayed in the river but his spirit lives on. All in my opinion.