Reading over this thread, I am reminded that TH had her baby daughter with her that day. So if she left with Kyron, that would have been a bit of a parade, and hardly likely to have gone unseen by anyone. I don't know what happened to this dear little boy, but I continue to believe that he couldn't have left there with his stepmother. The timeline just doesn't make sense.
I've never imagined that the three of them walked out a doorway together. I have imagined other scenarios in which the three of then ultimately ended up back in the truck together though.
I've considered that 1. she could have sent Kyron back to the truck where someone, a, co-conspirator was waiting. 2. She could have sent him out to the truck alone and told him to get in and wait for her. 3. She could have gone into a bathroom with all three of them, rendered Kyron unconscious and somehow smuggled him out in the stroller with baby K (I think this is less likely) 4. She could have sent him out one door and herself gone out another to meet him. 5. If she had a co-conspirator she could have had that person waiting right outside the door that she sent him out.
I imagine any of these scenarios involved waiting until all the kids were in their classrooms and the bell had rung, or almost rung. I'm sure she timed her plan so that she was not likely to be seen, and I'm sure she also was lucky that her plan worked and she had an opportunity and a clear shot to do it (send him out unseen… or whatever she did)
I'm sure he would have done whatever she told him to do, especially if she was using a cover story that involved a doctor appointment that was arranged for a deliberately confusing date.
I don't pretend to know exactly what happened, but I don't find it at all impossible that she had a plan in mind, she hoped for an opportunity to make it work and the opportunity presented itself and when no one was looking, she took it.
I will say, that even early on, but more so as time passes, I struggle with her having a co-conspirator. It's hard for me to imagine why anyone would agree to help her with a crime of this nature. On the other hand, I've read enough news stories about pairs of people committing heinous crimes together that I know it does happen: the skylar neese murder, the columbine high school shootings, Jaycee Dugard…. So, there are times when two people will work together to do something awful. <shrug> that doesn't prove she had help, it just keeps me from ruling it out altogether.
I don't know what happened, but it's not impossible, in my mind, that she persuaded Kyron to leave the building somehow unseen and that the three of them drove away together.