Theory:
CPS visited the family in December. Investigating something that turned out to be un-provable about the father and his treatment of Isa, but serious enough that a person close to them who adored Isa decided she had to be removed for her own safety.
This person takes Isa, figuring either the mother didn't act to protect her or would not even with a divorce be able to keep Isa away from the dad. This abduction happened with or without the mother's knowledge, but maybe the mother has figured this out and this explains her calm Mother's Day appearance when she/her sons look forward to being together as a family, with Isa (no mention of Sergio). It could also somewhat explain Sergio's demeanor on the phone; he thinks it's a joke or something over which he will scold his wife ("I told her to get her butt home") and maybe his reluctance to call 911 in the first place (Becky would have insisted he did, which leads me to think she didn't know the abduction was going to happen). It also explains their reluctance to talk to the media and their "we want to keep this about Isa."
So, the question becomes: Who knew about the allegations that resulted in the first CPS visit?
Of course, part of the reason I like this scenario so much is it leaves open a possibility that Isa is alive and not being hurt.
With my new theory in hand, I went back and re-watched the parents talk to the local media and I also re-watched RC's Mother's Day interview. VERY interesting.
A few thoughts --
1. As Sergio laughed during the 911 call, he also laughed during the long interview when asked, "What do you say to the people who wonder if you had anything to do with Isa's disappearance?" (question paraphrased) He laughs twice during his answer. This has nothing to do with my theory, but I wanted to note that!
2. On Mother's Day, when interviewed outside her house (which I maintain was deliberate; she had to know she'd be asked for an interview), she makes it clear the boys are with her (because the public had been speculating which parent got custody) and that she hoped Isabel would be home for Mother's Day. "But I don't know the plan." To me and my theory, it obviously seems she believes there IS a plan, and she wasn't a part of it. As many people have commented, she also seems way more relaxed than previous times we've seen her, maybe because she now believes the person who took Isa does not intend to harm her. Had she wanted to show unity with Sergio, she could have had both of them go into the house (as long as the kids weren't around), but she didn't. She wanted to make it clear she was standing on her own, waiting for "the plan" to unfold.
3. If my theory is correct, that the person who took Isa did so because she/he believes Isa was being abused and RC nor CPS was doing enough to stop it, then the first interviews with the parents must have completely irked the abductor because what was presented above all else was a unified front between the parents. And Sergio talked and talked about his new camera and how he took so many pictures of Isa and her new dog - if I were the person who called CPS - if it was in RE: to Sergio - I would be furious to hear him talk that way. And cuddling with the boys and holding them tight....
All these other things being announced in the press - that Sergio was not permitted contact, that CPS had been at the home before, (again) RC standing alone not talking about Sergio - could be a way of sending a message to the abductor - "we get it now." "We will pursue this path you wanted us to pursue before."
People thought Sergio's comment, "Tell us your demands" was odd, but it's true that an abductor WOULD have a motive/reason, and maybe the DEMAND is actually, "Get that guy away from Isa." And that demand is now being met.
4. And what was Becky sneering about throughout that whole interview? I'm sure she hated having to do it, but could the sneer also have been for what Sergio was saying?
"Bring Isa Home."
Any thoughts, anyone? In any case, I do urge everyone to go back and watch what the parents have said again in light of the past several days' events. It might help us all see new things we missed before.