Police were alerted to the alleged crime after a group page went up on Facebook: "Independent Fundamental Baptist (IFB) Cult Survivors (And their Supporters)."
Matt Barnhart, a former member of Anderson's church, left a simple message: "Trinity, New Hampshire, church hid 15-year-old getting pregnant from deacon. You can contact me privately."
The site supervisor, who runs an advocacy group for Baptists, Freedom from Abuse, alerted Concord police who culled information from a high school friend of Anderson's to locate her.
Anderson, who at the time was teaching voice at the International Baptist College in Chandler, Arizona, got the police call out of the blue.
"Right now I feel completely overwhelmed," said Anderson. "It's been tough. In my mind, I didn't think he'd be arrested, and when I got the phone call I was completely shocked. My whole world has changed."
Anderson agreed to press charges.
In a prepared statement last week, Trinity Baptist Church, which has new leadership, told the Concord Monitor that at the time there were many documented calls to the police to report the alleged rape and the names of those accused of being involved, including Willis.
The church said a report was made to the Division of Family and Child Services within 24 hours of learning about the accusations on Oct. 8, 1997.
"Trinity Baptist Church was the first to report this crime in 1997 as well as the only one to give repeated reminders to the Concord Police Department," the statement said. "We continue to be committed to assisting in the investigation in any way possible."
Phelps, 51, who now preaches at the Colonial Hills Baptist Church in Indianapolis, Ind., did not return calls from ABCNews.com.
His receptionist said Phelps has retained a lawyer through the Christian Law Association, which did not return calls from ABCNews.com.
He told the Monitor that there was no church cover-up and he had immediately reported the accusations to authorities.
"I was the first one to report this to the police, as was my duty," he said. "The people who didn't do their job was the Concord Police Department."
He also said that Anderson's confession was not discipline, rather an opportunity for the church to help Anderson.
"Church discipline is the removal of a person from the assembly," Phelps said. "This was not that. This was a chance for people in the church assembly to embrace her, and they did."
Anderson said she told both Phelps and her mother that she didn't want to go to Colorado and wanted to live with her paternal grandparents in Texas.
"My mother is very much a follower," said Anderson. "She believes she needs to do what [the church] tells her because they are men of God. But I don't think she made the wisest choices."
Anderson was sent to live with a family who worshipped in an IFB parish where Phelps had been a youth minister. Its pastor, Matt Olson, who is now president of Northland Baptist Bible College in Dunbar, Wisc., to write a letter to Willis's wife to apologize, according to Anderson. Two church members were also at her side in March 1998 when she gave birth to a daughter. Phelps urged her to give the child up for adoption, she said.
Anderson's traumatic journey began at the age of 11 when for two years she says she was sexually abused by her stepfather, who with her mother is still an active member of Trinity Church.