The mother of missing Milton Keynes girl Leah Croucher says it is "unbelievable" she has not been in contact with friends or family for more than a week.
In an emotional appeal, Leah's parents said they are "beside themselves with worry," after she went missing from home on February 14.
The last sighting of the 19-year-old was the following morning at Buzzacott Lane in Furzton, Milton Keynes, just after 8.15am.
Her parents, Claire and John Croucher, said her disappearance is "highly unusual" as they appealed for information seven days after she was last seen.
At a press conference on Friday morning, Mrs Croucher said: "She mainly chooses to communicate with her friends through social media or text.
"It's unbelievable to her family and friends that she would choose not to contact any of us for the past seven days in any of the formats that are available to the youth of today.
"She would not wish to cause worry or the fuss that has arisen due to her highly unusual disappearance.
"She is a creature of habit who loves her home comforts."
Pausing to compose herself, Mrs Croucher added: "Leah, if you are able to hear or see me as I read this, please, please get in touch or, better still, come home.
"It doesn't have to be me or Dad that you contact.
"You can call, text, email, Facebook or Snapchat anybody you feel comfortable with getting in touch.
"Just show us that you are safe.
"Your family, friends, work colleagues and the taekwondo community across the world are extremely concerned for your welfare.
"Just drop someone a call to say you are OK.
"We are beside ourselves with worry."
Thames Valley Police Chief Inspector Neil Kentish said there have been two unconfirmed sightings of a female who "may be Leah" in the area of the Teardrop Lakes at approximately 8.45am on February 15, and that searches are being carried out.
"It is totally out of character for Leah to go missing," he said.
"She hasn't spoken to her family and friends, she hasn't used her mobile phone or accessed her bank.
"She hasn't used social media.
"We need your help to find Leah. Have you seen her? Have you spoken to her? Do you know somebody that's spoken to her or has met her?
"We would like to hear from anybody with CCTV or dash cam footage from Furzton, Emerson Valley, Shenley Lodge, Knowlhill and surrounding roads on Friday the 15th between 8am and 11am."
The family were due to embark on a holiday in just two weeks time, the teenager was "excited" for the trip and had helped pick hotels, Mrs Croucher said.
Leah was last seen wearing a black coat, skinny black jeans, black Converse shoes and carrying a small black rucksack.
Police have knocked on more than 4,000 doors in Milton Keynes as they search for clues to Leah's location.
Thames Valley Police Chief Inspector Neil Kentish asked members of the public to come forward with an information that may relate to her whereabouts.