Dilip, a jeweller belonging to Thrissur, who was travelling by bus from Karkala to Mangaluru, was looted at night by the robbersposing as policemen.
They pushed him out of the bus, forced him into a car and took away gold and cash worth Rs 42.57lakh, before leaving him at Padubidri.
Police said six persons were involved in the robbery and the hunt for the sixth was on.
They suspected the role of a jeweller in Perdoor near Karkala, to whom Dilip had sold a large quantum of gold, behind the robbery, police said.