I'm sure they knew, but there are so many factors. One, *because* they knew her past, they also knew *she* would know she'd be high on the suspect list, and may have figured the last place she'd have hidden Shannon (dead or alive) was in her own house, since it was so likely to be searched (and I don't think we know for sure that Shannon *was* in that house the whole time she was missing). Also, with Shannon alive, there wasn't a whole lot search dogs could determine re the house, because it was known that Shannon regularly spent time there with her "babysitter", including very recently, so her scent would have been all over the house, even if she wasn't there at the time the dogs were sniffing around.
They may have figured (and possibly correctly, at first) that if SB had Shannon, dead or alive, she had her hidden somewhere else, and were hoping that by leaving SB more or less alone, she'd be more likely to lead them to her. I'm sure they had her under very heavy covert surveillance. At some point, they may have been tipped off that Shannon was alive and in the house, by observing the purchase and transport of baby food or diapers to the house, or, as I suggested on a previous thread, they may have gotten a listening device into or very near the house, and picked up sounds consistent with Shannon periodically being brought out of hiding for feeding and diaper changes. If they had any reasonably solid reason to believe Shannon was in the house, alive, *and* being cared for, given SB's history of violent child abuse and probably rold in the unsolved disappearance/presumed murder of another child, they had to be very, very careful not to do anything that would tip off SB that they were on their way to search the house, until they could get themselves physically between SB and Shannon. SB could have *very* quickly killed Shannon (to shut her up and make her easier to keep hidden during a search), and from what we know (and LE knew) of her history, probably wouldn't have hesitated to do that, if she thought it improved her chances of not getting caught.
I'm confused by the delay of approximately 12 hours from the time they got SB and JB to the police station, and the time they went into the house to start doing a thorough search, but I think there must have been a reason. I can't see a judge refusing a search warrant for that long, and they ultimately got permission from SB and JB to search the house (and got a warrant too, but only needed that in order to remove what they found). Maybe they still thought it was likely SB had hidden Shannon somewhere else, and wanted to keep her cooperative and believing that were still thinking someone else might have been responsible for Shannon's disappearance. Remember they knew that another child who had been in SB's care had disappeared and *never* been found, dead or alive, and that may have been something they were really trying to avoid repeating.
LE had some very scary choices to make, and I'm sure they had to make a lot of tough calls where they weren't sure if they were making the right call. But I really don't think they did anything stupid.
