We received an anonymous call from someone telling us its location," he said.
"It seems to be in good order."
Pc Roberts said the car had now been towed to a vehicle compound and will probably be returned to the insurance company.
He added: "I'd love to think Harry himself had driven it there to take part in some adventure at the castle but the reality is probably a little less interesting."
The Anglia - registration 7990 TD - is pictured on the front cover of Harry Potter and the Chamber of Secrets.
It used to take pride of place at the gates of South West Film Studios but vanished one night last November.
The company had gone into administration and the car was being stored under a tarpaulin while a private buyer was sought.
Carn Brea Castle bears a striking resemblance to Hogwarts School of Wizardry and Witchcraft.
Scientific experts were examining the car yesterday. A length of rope that was found attached to the back could yield vital DNA and help to solve the mystery.