A cop who happened to be visiting the museum was the first to notice a work was missing from the Nicholas Roerich Museum on West 107th Street near Riverside Drive.
It was 30 minutes before closing time on June 24 when he saw a blank spot on a wall where a picture was supposed to be.
"A police officer was just visiting, and he noticed there was a label and no painting," said a museum employee.
Gone was a $20,000 piece called "The Himalayas," a 10-by-14 inch pencil-on-paper drawing that Roerich, a Russian artist, sketched to mark his days in the 1930s when he was living in the foothills of the Asian mountains.
But then four days later an employee noticed "a work was missing from a wall in the same hallway, a 12-by-16 inch oil-on-canvas painting called "Talung Monastery," valued at $70,000." The difficulty the museum had in discovering the theft of the works probably speaks to how the thefts took place. The museum has only four staff, and receives about 25 visitors daily.