The Standing Figure was taken from Glenkiln Sculpture Park on Lincluden Estate, Dumfries and Galloway last week.
Detectives said a group of men in a Ford Transit-style van were previously seen looking at the bronze, worth £3 million.
The three men are thought to be in their 20s or 30s, of average height and build and were accompanied by a collie-type dog.
One of the men had ginger, shaven hair and was wearing a red or orange waterproof jacket.
The van they were in was described as being an "unusual" shade of blue.