The InterCity bus driver who left a young boy behind at a South Auckland service station had a "very heated" phone conversation with his boss moments after driving away.
Bill Randall-George, 68, was sitting just in front of the boy and two rows back from the driver when the incident occurred on Friday.
He claims the driver's version of events, as told to his boss, was very different from what actually occurred.
The company has since apologised to the boy's family, refunded the ticket and launched an investigation into the incident.
Randall-George said a passenger opposite him told him to eavesdrop on a phone conversation between the driver and his boss after ditching the youngster at a Bombay bus station when the boy had got off to use the toilet.
"She told me to listen to what the driver would tell his boss about what happened...it was completely different to what happened, I couldn't believe it," Randall-George told the Herald.
The 12-year-old boy was travelling from Tauranga to Auckland when the bus made a stop at the Bombay station.
He asked the driver if he could use the toilet and the driver replied that the bus was only going to be stopped for two minutes.
Randall-George said the boy was clearly distressed and urgently needed to go to the loo.
"He was very polite and a likeable chap but the driver was very rude.
"The driver told the boy 'if you get off the bus I may or may not be here' and like any kid the boy took that as 'be quick'."
Randall-George said the kid sprinted to the toilet but the driver took off before he returned. The boy's luggage was still onboard the bus.
"A young girl who had been sitting with the boy raced up to the driver and told him the boy wasn't on the bus but the driver rudely dismissed her," Randall-George said.
The driver then rang his head office and it was a "very heated conversation" while he tried to justify his actions, Randall-George said.
The driver told his boss the boy had run off the bus and run away, Randall-George said. There appeared to be no mention of the child needing to use the toilet.
"We all couldn't believe it . He could have waited one or two minutes and there would have been no dramas but he just took off.
Intercity called another bus which picked the boy up sometime later.
"He was lucky it all worked out because it potentially could have been very dangerous," Randall-George said.
The company has previously acknowledged the incident and said they are investigating.
The company's general manager Sam Peate said tonight: "We are unable to comment further until a full investigation has been conducted."