The hired craft was found tied to a tree near Salhouse Little Broad on Saturday evening.
Officers closed a mile-long section of the River Bure between Salhouse and Wroxham broads as they searched the area.
The girl was unharmed and spent the night in protective police custody. She was due to be spoken to by specially trained officers yesterday.
The police examined the vessel at the Le Boat boatyard in Horning Norfolk Police said they had a call at 5pm on Saturday from a member of the public who was concerned that the hire boat had not been returned as arranged.
After it was found, the boat was returned to the Le Boat boatyard at Horning for examination by the police. Officers closed the river in the early hours of yesterday in consultation with the Broads Authority.
Local residents yesterday said the disappearance occurred after the cabin cruiser they were renting from a firm named Le Boat broke down. When one parent did not return, the other set off to find them, locals suggested.