Beneath the calm prose, you can feel the family trauma that may have caused a child to run away. Ms X's sister had died in an accident just before she left.
Ms X is just the sort of girl in whom Frederick and Rosemary West would have been interested had they chanced upon her waiting at a bus stop around Gloucester. She was only a little younger than Juanita Mott, who left an unstable home for a variety of bedsits before ending up decapitated and dismembered in the Wests' cellar. And there is no shortage of girls like her among Britain's disappeared. Each week, the Big Issue runs four new cases in its "missing" column. At least one of them usually concerns a young woman. Many, like a number of the Wests' victims, have been in council care. They are vulnerable, lacking family support. But they have no wish to return to what they fled.
"Fourteen- and 15-year-old girls are twice as likely as boys of the same age to run away," according to Sophie Woodforde, of the National Missing Persons Helpline, which runs a national register of missing people. "They mature more quickly and some get frustrated at home. They get an older boyfriend and run off. Or they have an argument with the parents and they can't cope, so they leave."
The vast majority are found alive and well. But the wait for news can be long. As time goes by, fear rises that they have been killed. Dinah Marie McNicol disappeared in August 1991, aged 18. She was hitchhiking to Portsmouth from a music festival. She was last seen on the M25 near Reigate. Her cashcard was used that August in Hove, Havant, Brighton, Portslade, Margate and Ramsgate. Each time pounds 250 was taken out. There has never been any other clue as to her whereabouts.
Disappearances are not confined to girls who run away from home. Every month also brings fresh instances of women who disappear, apparently without a trace. Jane Harrison was last seen by her boyfriend on 15 June, when he dropped her off at her mother's home in Highbury, north London. Jane, 32, never reached the house. She left behind a 20-month-old baby and a 15-year- old son. "Jane lived for those kids," says her sister, Clare. "We just can't make out what has happened. Jane had lots of friends: she was very attractive, the sort of person who goes down the road and says hello to everyone.
"Jane had no money or spare clothes with her. Nothing has gone out of her bank account. We've checked airports, hospitals. The police have done door-to-doors and reconstructions. We've even called in a psychic who is convinced she's alive. There is nothing we can do. It's been five months now. The oldest boy is taking it very badly. He's withdrawn, a changed personality. Some of the kids at school taunt him, saying his mother has run off or they've heard she is dead. We just sit and wait. If she is out there, then, please God, she will be back for Christmas."
Diana Goldsmith's disappearance earlier this year is equally mysterious. Ms Goldsmith, 45, was last seen by her three children as she dropped them off for school in Sevenoaks, Kent, on 25 January. She did not pick them up that afternoon and has not been seen since. She was wearing blue jeans, a light-blue denim jacket and carrying a black handbag. Even a reward of pounds 25,000 has not produced helpful evidence. Two days after her disappearance, Ms Goldsmith's car, a white Volvo 440 SX1 was found abandoned in a nearby multi-storey car park in Lakeside, Grays.
Ms Goldsmith had a drink problem. According to her twin sister, Linda Curry, she was very insecure and lacked self-confidence. "When she was under stress, she would hit the lager at lunch time. She had split up from her partner two years before and there had been a long battle in the High Court over the kids. I rang her the weekend before she left: she was very drunk. It is possible that she got drunk and someone attacked her.
"It is in the character of my sister to disappear. She was under so much stress and strain that she may have needed a break. But she has drawn no money from the bank. The police have interviewed 1,000 people, but they've found no clues."
Often, the alarm is not raised until long after a person has gone missing. In a recent case, the National Missing Persons Helpline (NMPH) received a call from a woman in Leicester wondering about her sister, last seen 15 years ago. Her disappearance had never been reported to the police. It turned out that she had been murdered and buried beneath a garden pond by her husband.
It is impossible to get accurate figures on missing people. But in London alone in 1994/95, the police say more than 20,000 people under 18 vanished. A quarter were under 14. Of the total, more than 200 have not yet been found. The NMPH receives 80,000 calls every year from people seeking help. It estimates that 250,000 people are reported missing every year, 100,000 of them under 18. Most are found alive and well. But more than 14,000 people are currently on the register, 17 per cent of them under 18. The NMPH hopes to resolve 60 per cent of the cases. It is thanks to this register that four of the bodies found in Cromwell Street - those of Alison Chambers, Carol Cooper, Juanita Mott and Therese Siegenthaler - were identified.
The missing disappear for a host of reasons, says Sophie Woodforde of the helpline. "Young people may be suffering abuse at home or being bullied. Sometimes young boys are enticed by older men. Women may leave because they are suffering post-natal depression, some sudden trauma or they have lost a job and not found another. Older men make up a huge group and may leave as an alternative to suicide. They might have a mortgage and a young family and can't face telling them when they are made redundant. They are often found or come back or do actually commit suicide. Then there are older people suffering from Alzheimer's disease or dementia who get lost."
Occasionally, though, the pattern of disappearances causes extra concern. Recently, the National Missing Persons Helpline surveyed its outstanding cases in a particular English county. The picture was worrying. Nationally, missing men outnumber women two to one, but the pattern found in this county was very different. Twice as many women as men are unaccounted for in that area.
These figures are probably a statistical accident, but they are enough for the police to have begun investigating whether there is a sinister link between them. Such attention to trends can pay dividends: a recent survey of another county spotted an unusual cluster of missing boys. The police were notified and have identified a paedophile ring. But despite all the cross-checking, electronic data bases, detection work and equipment that can enhance the age of a face fixed on film, many of the missing remain elusive.
Sometimes, though, there is a happy outcome. Last weekend, after 17 years, Ms X was finally reunited with her family.
The National Missing Persons Helpline is funded solely from charitable donation. Its freephone number is 0500 700 700. Message Home is a confidential freephone number for anyone missing who wishes to say they are alive and safe: 0500 700 740.