Meant to include some of this in original post, but got distracted and forgot. Works as a reply, anyway, though.
From memory of the CIA episode that was done on this ten years ago, Sarah's disappearance wasn't reported until a couple of days after it happened (Monday morning IIRC) when her sister realised she hadn't been around for the whole weekend and she called her work and she wasn't there.
That's already a long timeframe to begin with, especially factoring age, character, level of responsibility, no friends having seen her.
It could also be the area it happened. It has been said that one of the reasons this case has attracted so many resources is because it was Claremont, and I tend to agree with that. Not saying police wouldn't have done a thorough job if it had happened elsewhere, but I think this has always been regarded a bit differently.
Beyond that, though, any evidence they had to prompt such a significant investigation so soon may not have any significance now. There was the report regarding the taxi and the black-haired good looking guy from the morning beforehand.
JMO
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