Sightings of it have been reported too, between Ashburton and Christchurch.
Campey said he and his partner went to take the dog for a walk on Monday and noticed things were out of place.
The gate was open, doors were unlocked and a window had been broken.
"I thought, yep, we've been robbed," Campey told Newstalk ZB.
"They've moved a lot of stuff around, drawers have been opened and eventually found the keys to the garage and taken off with the Mustang.
"I've had a lot of people message me saying they saw it going northbound towards Christchurch around the airport and Hornby around 4.30 [on Monday afternoon].
"It's awesome. I can't say thank-you enough to everybody that has put forward their support."
He said he was hopeful - but realistic - about the chances of the car being found.
"I would hate to see it burnt out or parted out [broken up for parts]. That's not what anybody wants to see for a beautiful car like that."
Campey had phoned his father to explain the loss.
"He just took a few moments to clear his head. He took the phone away and I think he said a few swear words. He came back to it and he was pretty calm about it."
The police said they had received a report on Monday evening about the car theft. The Ashburton property was visited, forensic and area inquiries were made, and the investigation was ongoing.