Here you go - my post, please point out which bits you consider "improbable events"?
As far as I see it - she was concerned that night (but not fearful of the twins imminent death), but had more pressing worries in the disappearance of her eldest child, and her concerns for the twins took a back seat to the other major issue by morning when they were fully conscious and behaving normally.
If she thought, as she did, that the twins may have been sedated and she knew, from her training, that the drug that may have been administered may slowly have been having catastrophic effects on the children's bodies so how could she not be fearful that it may be fatal? That she was lucky that they were hail and hearty in the morning does not negate the almost unfathomable decision she made the night before.
Further you say that she had more pressing worries but she found time to pray. Wouldn't that time have been more constructively used trying to seek medical attention for her babies ?
It's bit like saying I won't jump into the water and save my drowning child because I'm already worrying that my other child hasn't come home yet. It just doesn't make sense.
Just in case there is any doubt that Kate was afraid for the twins life this is what she wrote :
"I wandered into the children’s bedroom several times to check on Sean and Amelie. They were both lying on their fronts in a kind of crouch, with their heads turned sideways and their knees tucked under their tummies. In spite of the noise and lights and general pandemonium, they hadn’t stirred. They’d always been sound sleepers, but this seemed unnatural. Scared for them, too, I placed the palms of my hands on their backs to check for chest movement, basically, for some sign of life. Had Madeleine been given some kind of sedative to keep her quiet? Had the twins, too? It was not until about 11.10pm that two policemen arrived from the nearest town, Lagos, about five miles away. To me they seemed bewildered and out of their depth, and I couldn’t shake the images of Tweedledum and Tweedledee out of my head. I realize how unfair this might sound, but with communication hampered by the language barrier and precious time passing, their presence did not fill me with confidence at all."