There had been several reports of it being seen, ranging from on the water in the Bay of Islands, around the Snells Beach area and also being towed by a 4WD vehicle near Dome Valley and on the Northern Motorway.
However, those reports were unconfirmed.
A sighting was also reported from as far away as Te Puke, but after an investigation it was found to be a different barge, Ms Knowler said.
Police had put a photo and the vessel's details in media around the North Island and on the Police Ten 7 Facebook page in the hope that someone would recognise it and get in touch.
Ms Knowler said it was not yet known, at this stage, whether the barge had been stolen or if it had broken its mooring.
"It may be difficult after all this time to determine how the barge ended up so far from home," she said.
"I'd like to thank Ross in Australia who found the barge and made the effort to find out where it came from. Many people would not have bothered to do that. I was very surprised to get a phone call from a previous owner, who had been contacted by Ross, to say the boat had been found."