The British prime minister and his wife Samantha forgot about their daughter Nancy after a pub lunch for about 15 minutes, reports The Sun.
Nancy is said to have walked off to the toilets while the Camerons and their family and friends were organising lifts.
It was only when the pair arrived home that they realised their error and immediately drove back to the Plough Inn in Cadsden. However, Nancy was soon afterwards discovered with staff at the pub safe and well.
The incident took place a couple of months ago, but has only just been reported.
A Downing Street spokesman said: "The prime minister and Samantha were distraught when they realised Nancy wasn't with them.
"Thankfully when they phoned the pub she was there safe and well. The prime minister went down straight away to get her."
The Camerons were also at the pub with their other children and two other families. David Cameron left the pub in one car with his bodyguards, while Nancy was presumed to have been with his wife and the other children.
However, it is thought that Samantha Cameron had in turn thought that Nancy was with her husband.
The prime minister will be called up to appear at the Leveson Inquiry later this week along with Nick Clegg and Gordon Brown.