Waipu police Senior Constable Martin Geddes said the boat operators saw the rescue and went out to sea to have a look. When they towed the jetski to Uretiti Beach, they were approached by two men.
The duo claimed the abandoned jetski was theirs and that they'd travel to Mangawhai to get a trailer. They never returned to pick up the jetski.
Mr Geddes said the thundercat boat operator picked up the jetski, washed and stored it in his Waipu home shed.
A second jetski was stolen from the businessman's Langs' Beach home on the evening of their rescue. Mr Geddes said there was a possibility it was stolen by the two men who had earlier claimed to own the jetski.
The stolen jet ski is a 2006 three-seater Yamaha VX Deluxe blue-coloured cruisers with back hulls.
Anyone with information can speak to either Mr Geddes on 09 432 4030, Constable Daniel Hales on 09 432 7719, or to Crime Stoppers.