Joao Francisco, 44, of no fixed abode, was convicted at Snaresbrook Crown Court on Monday, 7 December.
He is due to be sentenced in January 2021.
Police were called after the 16-year-old victim reported that he had abused her in October 2017.
He had already been charged in June 2019 for sexual activity with a child but had failed to appear at court in July 2019. Enquiries began to locate Francisco, including a public media appeal in October 2019.
Investigating officers were called by members of the public who wanted to pass on information, before Francisco handed himself into a police station in January 2020 after seeing himself on the internet.
Following a one week trial, he was found guilty.
Detective Sergeant Jasmine Abbey, East Area Command Unit, said: “I am glad that Francisco has been convicted and I hope it provides some comfort to the young victim, who has shown a lot of strength throughout the process.
“I really do want to encourage anyone who has suffered sexual abuse to report it. They will speak with specially trained officers who are able to help them and investigate what happened. Please don’t suffer alone, we are here to help you.
“A media appeal resulted in a number of invaluable calls from members of the public, who were intent on helping us catch Francisco. I would like to thank every single one of those people who contacted us. It is imperative that police and the public work together to catch offenders and this is a prime example of how well that process can work.”