The loss came to the attention of mum Katie the following day, however she was unable to locate her daughter’s monkey friend.
Once back in Australia, Savannah’s school in Adelaide wrote Her Majesty in a bid to reclaim their beloved stuffed pet.
The letter asked the Queen to please search the palace for any lost jungle animals, and the students helpfully included photos of Harriet to ensure the monarch knew precisely which monkey they were seeking.
Imagine their surprise when their plea was responded to within week.
Not only was Harriet returned to the Great South Land safe and sound, the package included photos of the monkey living it up in various locations around the palace grounds.
One such happy snap featured Harriet enjoying a spot of jam and scones on the lawn. In another shot the long limbed toy cuddled Rex – a soft toy Corgi who accompanied her home.
Palace staff also included a children's book called Does The Queen Wear Her Crown In Bed?.
“We aim to give every visitor to Buckingham Palace a memorable experience and after we had found Harriet the monkey near the Family Pavilion, she spent some time helping out the Visitor Services team before heading home,” a Royal Collection Trust spokeswoman said.
“The look on her [Savannah's] face when she opened the box was priceless. She was so happy to see her [Harriet] returned,” said teacher Tash Hortle.