Maybe he called to see if he needed to be picked up?Maybe he assumed she had the son when she didn't answer? Why is that abnormal? Most fathers I know have very little idea of where kids are supposed to be and when they are supposed to be there.
My husband would have no idea the kids were left at school - even if the car was home. He would probably assume I went with my sister or my mother somewhere and took the kids. I find it strange so many people assume that he should have jumped to the worst scenario.... I saw in an interview he did that the school called him at 2 to go and get his son- if that is the case then he had 10 or 15 minutes to commit this crime and get his son according to the timeline he gives. I'm sure police have checked alibis by now. I've also read he has an air tight alibi. I know here police won't even take a missing person's report (unless it is a child) for several hours.... maybe he did call and the police told him to call back if she didn't arrive home by a certain time with the baby? They may have only accepted a report so soon because of the baby..... I understand he behaves awkwardly, but so does my husband and I think my husband would appear guilty (horrible anxiety issues) even if he was not. What a terrible thing to have to see comments like these on here if you are living through this nightmare and you are completely innocent.
I know it is easy to become jaded by tragedies like these, but there still is a presumption of innocence deserved.