: "She’s a very outgoing and independent young lady, but the longest we have ever gone without speaking to her before was two days.
"We can’t think why she would not want any contact, but we just want to know she is okay.
"She rang us from an unknown number to let us know her phone had been snatched, and we’ve been worried ever since."
Lilyanne left her flat in Lewisham around 10pm on November 10.
That was the last time she was seen.
Mark, from Shrewsbury, Shropshire, said Lilyanne has her mum's number memorised, and has previously rang her off friends' phones.
The teen called her mum on November 15, telling her she was in Peckham, but the call suddenly cut off.
Lilyanne moved to London to live near pals after studying at Birmingham University for a year.
Mark said it's Lilyanne's birthday on December 21, and usually she spends the day with him, her mum and sister.
He added that the Met Police are scouring CCTV but are yet to come across Lilyanne.
Mark - who has headed down to the capital to help with the search, told the : "It's been a living nightmare. Someone, somewhere knows where my daughter is."
He added: "I don't feel tired, I just need to be strong in case my little baby needs me.
"It's very out of character for her. The longest time without speaking to me or her mum is about three days."
The Met appealed on social media: "Can you help us find 19-year-old Lilyanne who is missing from Lewisham?
"She is about 5 ft 1, of slim build, with long brown wavy hair and a nose piercing on both sides."
Do you know more? Email ryan.merrifield@mcb777.fun