However, when the child asked the bus driver if he could go, the driver said the bus was only going to be stopped for two minutes.
"I think the boy thought he meant he would wait for two minutes and took off to [the] toilet," a woman posted to the Thames/Coromandel Grapevine on Facebook.
"Doors closed, bus driver started to drive off. A young girl ran up to the driver and said the boy was not on the bus.
"The driver said it was not a toilet stop, and he had told him he could not go, and drove away, leaving him behind."
General manager for New Zealand Coachlines and Auckland Tourism Sam Peate said InterCity acknowledged the incident took place.
Peate said an investigation into the incident was under way and they had spoken with the family of the child.
"The safety of all passengers, especially unaccompanied minors, is of paramount importance and an investigation is under way into how the incident occurred," Peate said.
"We were alerted to the situation and arranged for another InterCity bus to pick up the passenger within minutes.
"InterCity's operations manager has spoken to the passenger's uncle and offered our sincere apologies. We have fully refunded the bus ticket."
Meanwhile, the woman who posted about the incident online said she was appalled the driver would not stop the bus, leaving the child unaccompanied with his bags still on the bus.
The woman said she had laid a complaint with the company.
