This is maybe the most plausible theory I've heard. I think it most importantly includes Laura leaving with Samson. I think any compelling theory has to begin with Laura leaving the trailer with Samson. The reasons are twofold: One, she's left with everything she would need to have Samson with her overnight: baby blanket, cooked rice, bag with belongings. She's worn extra layers- the sweatpants and jacket, in case she has to sleep outside with him- or just to help keep them bundled up with night temps. Her intent is to sleep outside, or maybe she doesn't know where she's going to land, which also explains the knife. Laura is used to sleeping in tents and shelters etc., she's going to be well prepared.
But even more compelling to me is the bogus idea that Laura would leave the trailer, with a baby who is nursing and cosleeping (ie a baby who is 100% going to arouse at some point, then fully wake if he doesn't find mom and an opportunity to nurse) would leave her baby UNCONTAINED and UNSUPERVISED on the wide open trailer floor. Ie, she's going to leave him not in a crib or some sort of safety gate, and not let Tony or Sarah know she's leaving. Laura was not neglectful, and not intoxicated. No competent, fit, sober mother would do this. Again, that baby is going to wake up and have full, unsupervised access to the trailer to choke on something or hurt himself in many kinds of ways, even if the trailer is childproofed. Laura was about to open a daycare, she wouldn't have just overlooked this ginormous safety hazard she would be putting her toddler in. I'm not trying to point fingers at any particular person, or imply that people are lying. I just think whatever happened, she took her child with her when she left.
Sidenote, I personally think Leeanne may be somewhat of an unsung hero in this story. She isn't perfect, but what Samson experienced must have been highly traumatic for a 14 month old, and Leeanne stepped up with play therapy, speech therapy, and meetings with a psychologist. The podcast mentioned some of these were biweekly appointments, and that is no small task. Taking him to California was likely her way of removing him from a toxic and traumatic environment. Props to her.