"I drove off once with my groceries still sitting in the Kroger parking lot. Fortunately I never forgot my children."
I left the store without the groceries TWICE! (son 3yr, twins less than 1 - I remembered them! - sleep depravation was a big part of it!)
A couple of times I would look in the back seat of the car and go - where are the kids? Then remember that my wife had them with her. (whew!) Especially when changing the routine a bit, or dropping them off somewhere and then mom picking them up, etc.
It says the Dad showed up at the daycare later. I wonder if he was the usual person to take the child - and Mom "spaced out". Very tragic for the child no matter what was going on.