The 15-year-old had packed some clothes and left home to stay in her 27-year-old boyfriend's Tampines home.
The two, who had entered into a relationship the day before, subsequently had sex multiple times before the girl's cousin spotted her two months after she had gone missing.
The cousin then informed the girl's mother,who confronted the man and lodged a police report.
Yesterday, the man was jailed 35 months for two counts of sexual penetration with a minor, one charge of consumption of a controlled drug, one charge of possession of a controlled drug, and one charge of theft in dwelling.
He had been caught with a straw containing morphine at Tampines MRT station on June 18, 2010.
On July 27, 2010, he entered the office premises of his ex-company after he was fired, and made off with a laptop.
The court heard that the man had got to know the girl sometime in 2009 through a mutual friend.
They started chatting over the phone. He found out about her age during one of these conversations.
On Oct 17 that year, the girl asked him if she could stay over at his house and he agreed.
Stayed with him They subsequently had sex in his bedroom that night.
She continued to stay with him until Dec 13 that year, when her cousin spotted her.
The man is an inmate at the Drug Rehabilitation Centre, and had previously spent seven years in corrective training.
This article was first published in The New Paper.