William Binsley, who has a track record of attacking lone women, was months away from being removed from the sex offenders register when he attacked his teenage victim on a canal towpath in Walsall.
He grabbed her by the throat, forced her to the ground and held a hand over her mouth before assaulting her on a pathway off Green Rock Lane, in Bloxwich, on July 24 last year.
The victim feared she would be thrown into the canal before Binsley fled with her mobile phone, bank card and headphones, Wolverhampton Crown Court was told.
The 44-year-old was later tracked down by his car, which he had parked near the scene just before the attack took place. The victim also pointed him out in an identity parade.
Binsley, of Bloxwich Road South in Willenhall, was charged with sexual assault and robbery. He initially denied the charges before changing his plea to guilty days before his trial was due to start - and after his victim had already been cross-examined at a hearing.
Prosecutor Mr Matthew Barnes said: "Binsley approached her from the front, walked past on her on the path and nodded. As she walked away he turned and followed her, now wearing a face covering, which she described as a balaclava but was probably a black snood later found in his car.
"He put his hand over her mouth from behind and his other arm grabbed her around the neck. He removed her iPhone from her pocket, pulled her down to the ground, lying her on the grass, keeping his hand over her mouth. He asked her if she had anything else and in fear she gave him her AirPods.
"He then sexually assaulted her. He kept his hand over her mouth and was looking for passers-by. She pleaded with him to stop.
"She later said to police she did not want to die for her mobile phone. She did not know if she was to be raped, thrown into the canal, or kidnapped. He then fled the scene – and she ran away in shock and distress, and raised the alarm with a passer-by. She gave police a description of her attacker. She also sustained a small scratch to her face and mark to her wrist.
"Shortly after committing the offence, Binsley had telephoned his sex offender management and left her a voicemail message asking when she would be visiting him that day."
The court heard that the teenager now suffers "new levels of anxiety, questioning everything". She also feels vulnerable, views people negatively and is scared to be on her own, even at her home address.
Binsley had been convicted of similar attacks in 2012 and 2013.
Defending, Miss Marie De Redman said: "He has been required to be on the sex offenders register and was only months away to that coming to an end when this offence was carried out.
"His offending history has become known, he has been threatened, his front door kicked in, people have come into his house in the middle of the night and dragged him into the street - displeased that they have a sex offender living in the area.
"This does not excuse the offence. But it does go to explain some of the fear he had to admitting what he had done. That does not mean he is not ashamed of his actions, he is. He has taken some time to come forward to explain his actions – but he has now done so. He says it was opportunistic."
She added that at the time of the offence and throughout his life he had struggled with his mental health.
Judge Stephen Thomas sentenced him to 11 years and four months in prison for the sexual assault, with an extended licence of three years. His sentence for the robbery, 57 months, will run concurrently.
He added: "I consider it necessary to impose an extended sentence to protect the public."