I thought it was a detective Vanessa Patridge. IIRC, after the 1st day police were reporting back to the station that they thought something more sinister had taken place and she arrived on scene for the 1st time the following morning. When Michael Usher interviewed her on 60 minutes, her 1st thoughts were, "William's not missing", which she repeated that phrase and didn't clarify what she meant by it and it has always stood out to me, cause it was so profound, cause he is missing. One thing I've noticed about police is sometimes they mean exactly what they say and other people put there own inference on that. If he wasn't missing to the person who had reported him missing, then that person, it would logically follow, would know where he is. IMO
Another example of police literally saying what they mean was 1st responder Chris Rowley in the same program. He met the FF for the 1st time at the house, even though we were all under the impression that he was out looking for WT. I know that I thought, surely they mean in a general sense, like around the property, outside, but it was later confirmed in other media that Chris Rowley 1st encountered FF coming out of the bathroom at the house crying.