I don't discount that it was some kind of "mistake," , but I also think there is something seriously wrong with either the brain, parental instincts or priorities of someone who could forget about their child for that length of time, particularly given the "memory-jogger" of going out to the last place you saw your child a few hours later! I'm sorry he felt so desperate or so perfect that he had to lie, but if you allow these incidents to to go unpunished it becomes the perfect "excuse" for someone who WANTS to get rid of a child.
I agree - this would be a perfect way for someone who wants to kill their child. Usually, though, people who know the person immediately begin to realize it was purposeful - a serious custody battle, continuing to say if they didn't have the baby they would be in a better place, researching adopting the baby out, etc.
In this case, no one is saying that who knows him.
I think this is a dad who has hyper focus on work issues (as techies often do) and can switch one part of the brain off to focus on another. This is not a guy whose day care/no day care experience in the morning continuously crosses his mind.
Sad, sad.