Elspeth, it has already been established that the kids were having a sleepover with friends on that night. If you haven't been following the discussion here in detail from the beginning, there are a couple of things which were misreported or taken out of context at first, which have since been cleared up. One was the childrens sleepover location, the other was initial reports about the 10pm walk at night thing, but this was clarified fairly soon to reflect that GBC reported he last saw Allison at 10pm when he went to bed and she was watching the footy show. I am not sure which link, or links, to find all these details, it may be on the timeline, but as i recall GBC reported Allison missing to police at 7.30am after she didnt return from her mornig walk. This has been taken to mean that he is saying that he wouldnt have questioned her absence in the morning at first, because if she goes on a regular walk it could be reasonable to expect that on some mornings he may wake after she has left. So bascially he has reported her missing at 7.30am because she should have been back by say, 6.30am or 7am.
Others may be able to clarify if I've got this right, but I consider this is where we are now. some people have questioned why GBC would call police if Allison had been late back from her walk for only half an hour, or 1 hour maximum.
As for the news reports that he was frantically texting people as to her whereabouts, I'm not sure of the time he was supposed to have done the texting. I thought I read this very early on and it was when there was the confusion about her going for a walk in the evening. I think the report implied the texting was done in the evening because it prompted some discussion about why he would have then gone to bed if she hadnt come back. Personally i think this was misreported by journos extrapolating on the misinformation that GBC had said Allison went for a walk at 10pm.