Yes that is the normal default for everyone. The issue is when circumstances not entirely in your control make it not the default.
These study's point to three things that have occured in most of these cases that could remove your daughter from being on your mind constantly.
- Change in routine
- Stress
- Lack of Sleep
From the Washington Post article I linked earlier, here are the factors that led to this mother forgetting her child:
On the day Balfour forgot Bryce in the car, she had been up much of the night, first babysitting for a friend who had to take her dog to an emergency vet clinic, then caring for Bryce, who was cranky with a cold. Because the baby was also tired, he uncharacteristically dozed in the car, so he made no noise. Because Balfour was planning to bring Bryce’s usual car seat to the fire station to be professionally installed, Bryce was positioned in a different car seat that day, not behind the passenger but behind the driver, and was thus not visible in the rear-view mirror. Because the family’s second car was on loan to a relative, Balfour drove her husband to work that day, meaning the diaper bag was in the back, not on the passenger seat, as usual, where she could see it. Because of a phone conversation with a young relative in trouble, and another with her boss about a crisis at work, Balfour spent most of the trip on her cell, stressed, solving other people’s problems. Because the babysitter had a new phone, it didn’t yet contain Balfour’s office phone number, only her cell number, meaning that when the sitter phoned to wonder why Balfour hadn’t dropped Bryce off that morning, it rang unheard in Balfour’s pocketbook.
This anecdote has lack of sleep, multiple stressors and multiple changes in routine.
Every thing listed up there is a link in the error chain that led to the death of her kid. It's easy to point out how to break each link to prevent the catastrophe, but each link by itself is not enough to cause catastrophe, nor is each link easy to see when it's happening.
What the above tells me, and a career involving failure and risk analysis supports, is that in the presence of enough links anyone is susceptible to this.
Memory and evolutionary theory back this up as well. We have a prospective memory that helps us plan future events that's involved with our nice big prefrontal cortex. It's also expensive from an energy and evolutionary standpoint so we've evolved other structures to reduce that demand. We have a semantic memory that allows us to go on "autopilot" and do things we've done over and over again like driving to work without having to fire up the big expensive prefrontal cortex do them.
In her story above her prospective memory was first tasked with:
- Drop off Husband
- Drop off child
- Drive to work
Then say the troubled reltive called and it was
- Drop off Husband
- Drop off child
- Help relative
- Drive to work
Then she dropped off the husband and the boss called then it was
- Talk to boss
- Help Relative
- Semantic system takes over driving to work
What your post tells me is you feel that no amount of links in the error chain would be enough for you to forget your daughter. I disagree. All human brains are susceptible. Apply the exact right stressors, situations and links in an error chain and it could happen to anyone.