Shelley Pratt vanished on the way home from school five weeks ago.
She was last seen talking to an unknown man.
She was still in school -trousers and a purple hooded top with an I Love London slogan.
After talking to the mystery man, who also approached other women in the centre of Croydon, South London, -her Oyster travel card was used on another bus.
Shelley is described as 5ft 7in, brown haired.
She's had absolutely no contact with friends or family since her disappearance and it is possible that she may be with someone, perhaps in a house or a flat.
More top news
Londoners who have received new electronic gadgets for Christmas are being advised to take simple steps to protect them from thieves.
The Boxing Day sales got off to a flying start with shops reporting a surge in business during the first hour of trading.
Bus strikes are planned for Monday 29 December and Monday 5 January.