Parents said the teen, a student of Gonapinuwala Saralankara Vidyalaya, did not return home from school.
Her father said a youth had threatened the teen with a knife, a week before her disappearance.
The parents have lodged a complaint to the Hikkaduwa police. However, even after 46 days of the disappearance police has failed to take any action.
Hikkaduwa police said that an investigation is underway in connection to the incident.