Kate 'knew immediately'. That's a bit more definite than an 'instinctive feeling'. Most mothers with the slightest hope that her child had wandered would have to be held back from searching the resort from end to end, calling for her daughter until her voice gave out. Obviously I don't expect any supporters to agree with me. In their world she did the best thing by phoning lots of people to tell them of the 'abduction'; fait accompli.
They knew that many other people were already searching the resort. IMO Kate was in such a state of terror and stress at that time - I doubt if she was capable of calm rational thought. Her thoughts would be all over the place.
As I'm sure the Manager (can't recall his name at the mo) would have pointed out - the police had been called and so they needed to be there to speak to them when they arrived - not out searching. Once they did arrive their time would be taken up speaking to them.
If I found myself plunged into every parent's worst nightmare - I would desperately want to speak to my family - even if they were only round the corner - and not hundreds of miles away. I see nothing unnatural in that. I would also be praying to God for help - which IMO is something else normal people often do when they find themselves in a terrifying situation - even if they are not remotely religious.
IMO the idea that the McCanns should be thinking clearly and methodically at such a traumatic time is totally unrealistic.