Story highlights North Korean Mun Su Gyong disappeared four years ago while working in Cambodia

Her parents were told she was abducted by South Koreans who befriended her

South Korean government calls the claims "completely groundless"

Pyongyang, North Korea (CNN) Four years ago, Mun Su Gyong's parents in Pyongyang received a letter from their daughter, colorfully decorated with pink hearts, embellished with cut-out photographs of her. Because the majority of the country doesn't have Internet access, North Koreans still mostly communicate the old-fashioned way, in pen and ink.

The letter is now one of their most precious possessions -- a keepsake in the way that an email never could be. It was the last they ever heard from their daughter.

In the letter, Mun, who was 20 at the time, told her parents she would be coming home soon. Three years before, they had been proud to hear that their daughter had been selected to work overseas in a North Korean state-owned restaurant in Phnom Penh, Cambodia.

JUST WATCHED North Korea: From orphan to caregiver Replay More Videos ... MUST WATCH North Korea: From orphan to caregiver 02:58

Restaurants like these are important foreign currency earners for North Korea, which is cut off in so many ways from the international economy by harsh sanctions imposed on it due to its nuclear weapons program. The waitresses who work in these establishments are chosen for their beauty and their singing and dancing skills, but most importantly for their loyalty.

Disappeared

Read More