The Camerons had been out with their three kids and two other families at the Plough Inn in Cadsden, Buckinghamshire. When it came to going home they left in two separate cars - and both assumed the other had Nancy.
They quickly realised their mistake and within 15 minutes Samantha was back at the pub and reunited with Nancy – who was busy helping the staff.
That should be the end of the matter but the aftermath of the event has seen something of an outcry in certain parts of the media at this apparent lapse in parenting skills.
Think comments such as 'how could you do that? Walk away and leave a baby?' Of course there must be some political point scoring as the story broke on the day the Government relaunched its troubled families programme.
But while some parents may tut at such poor parenting I'm not sure I can see what the fuss is about. We are talking about an eight-year-old here and not a babe in arms (although that happens plenty too) for goodness sake.
When I was Nancy's age I would sit in the car with my brother in the pub car park while my parents had a drink inside the pub. Family friendly pubs weren't such a thing then and frankly coke in a bottle with a straw and a whole packet of crisps was a weekly highlight.
Since I have become a mother and auntie myself I can think of at least two 'doing a Cameron' occasions that I have been involved with.
Just last week we were on a family day out to a farm in Suffolk – the group consisted of six adults and eight children (always dangerous being outnumbered). Of course we did a lot of head counting but even so we managed to 'forget' my poor nephew Jack, eight, for at least 20 minutes.
His Mum Theresa, 37, explains: "I assumed Jack was with the other children in the hay barn so I was sitting down and chatting with some of the other parents. I'm used to him running ahead so it didn't cross my mind that he might still be in one of the fields outside."
It turns out Jack was still running around the farm doing a treasure hunt and hadn't noticed us go inside. Of course he was scared and a little teary when he was finally reunited with us 20 minutes later.
We did all feel slightly bad when we left the hay barn later and several parents came over and said how pleased they were that Jack had found us. In this case we were even worse than the Camerons as we hadn't even realised the poor boy was missing.
In another incident last year it was my daughter Leila, three, who was the victim of some poor communication between my husband and I. We were at the Bristol Balloon Festival and my husband went to find a spot on the grass while I said I would get the ice creams. Each of us assumed that the other had Leila in tow. As I returned with the ice creams we realised our mistake.
That awful sick feeling overtook me as I imagined the worst.
Thankfully it was probably less than a minute before I spotted her standing with another family about 50 metres away clutching another woman's hand.
The worst part of the whole episode was when the woman barked at me; "People like you don't deserve to have children." That comment still rings in my head when I do anything vaguely wrong as a parent.
Perhaps she did have a point but her response did feel a bit dramatic. I didn't purposefully set out to forget or lose her and I don't think anyone ever does.
A straw poll of mums reveals a plethora of similar stories. There is Alice, who left her five-year- old outside an art gallery as she assumed he was with her partner. Or Sian, who left her two-year-old in a supermarket trolley and actually drove out of the supermarket car park.
Even Mary and Joseph did it and it took them three days before they were reunited with Jesus in the temple.
Of course in all our cases we are lucky that nothing bad has happened, but in the end shouldn't we just give Mr Cameron a break on this one? He is only human after all.
Have you ever forgotten your children?
Thought a child was with someone else when he/she wasn't?