I think most of us have lost a child for a moment or two, or lost a pet and we do know what our first reaction would be. I lost my 2-year-old at a park one time and I was insanely searching, screaming his name, making a huge scene. I RAN full bolt for the nearest police station, but luckily ran past a Coke machine that he was standing in front of.
I can't say how I would have reacted if he has been missing for four weeks, but I think most of us believe that if we saw an empty crib, we would have woke the whole neighborhood in those first few minutes.
Some people do, I've seen that kind of reaction at Walmart, and I've seen other parents calmly search. But I agree an empty crib is different from a mobile child walking off, it's more of a concern.
First, Jeremy ran to the neighbor's house in case she had her. It may be that in that first moment, when Jeremy announced she was missing, Deborah's mind was racing to try to remember if the friend had taken her for the evening, wondering if she was somewhere totally innocent but knowing she might not remember it.