This is what confused me as well about the Amber Alert. I've seen them go on for days/weeks, so I was SHOCKED when this one was removed so quickly. I saw the Amber Alert being shared on twitter, when it was taken down, Sherin stopped trending. People assume if the Amber Alert is removed that the child is found and they stop looking and sharing because it is "old news". The first thing I did was google to see if she was safe and when I saw she wasn't my next reaction was to assume they aren't looking for her because they have found out she is deceased and to my knowledge Amber Alerts are only for living people, again we don't have anything confirming this theory either and it is confusing for the public. Either she is missing and should be assumed to be alived and searched for, or she is missing and people should be told to search fields and outbuildings etc as they presume she has passed. This feels like such a big cover up because we have NO CLUE what to be looking for. I know LE likely has a ton of information, but it's just shocking that they aren't encouraging the public to find her.
My take is that Amber Alerts are appropriate in a narrow range of cases. Many times I have seen them when there has been a known abduction and the general public can be alerted to a person, car or license tags. In the case of older children (who might be considered runaways) the balance is tipped if they are considered incompetent in some way or in need of critical medication.
I think that the deal is, there's nothing magic about the alert, it relies on people spotting something. Apparently LE is seeing nothing in this case to point towards possible abduction, and I would tend to agree. The likelihood of a random stranger driving through that back service road at 3 am and picking up a child standing by a tree in the dark is infinitesimally small. No custody fights or exes lurking in the background. Either Dad's story holds up and she was dragged off by coyotes, or someone in the household did something to her or took her somewhere. And in neither of those cases is an Amber Alert to the public to be on the lookout going to be of any help.
The FBI team--based on posted video--was doing a pretty thorough combing of the grounds (which makes me wonder about that FB journalist who says he found a hard drive under the tree after they had been there). I would imagine they did a pretty thorough search in the house as well--crawl spaces and all. And now they are analyzing all the stuff they took away with them--sorting through all the data that we all pile up in our daily lives--credit card uses, web searches, emails--to learn as much as possible about the people in that house and their recent activities; any indicators of foul play clinging to any surface in the house. Someone is analyzing those cars they hauled away--likely checking for DNA in unexpected places--like the trunk; anything helpful in the tire treads. Anything from any GPS devices.
And what I would fully expect to come next would be one or more searches in some other places, based on whatever picture they are able to piece together.
But I don't think cancelling the Amber Alert is a problem. They've just moved beyond the point where that would be helpful.