26-year-old Annie Riggs is at Las Colinas Womens Detention Center. 10News has learned she was in San Diego for her nephews military graduation when she turned herself in this past weekend, after a warrant was issued for her arrest.The Howard County Sheriffs Department in Indiana said this all began back in June 2009. That's when Annie and Brandon Riggs gave birth to their son, Brandon Jr.According to court documents obtained by 10News, Brandon Jr. was born addicted to Methadone and required extra care; care that the Riggs were not able to provide because of their own severe drug addiction.That's when Melissa and Stephen Lynch, known to sell prescription drugs to the Riggs, wanted custody of the Rigg's son. They had numerous conversations about price they'd have to pay to keep him as their own, and an offer was reached. Its reported in County documents that the Lynchs paid roughly $13,000 in cash, gave them $3,500 for a Lincoln Mark VIII car and 50 Oxycontin pills.Earlier this year, the Lynch's began the paperwork to legally adopt the now two year old boy. But a witness tipped off police to the sale and one week ago, an arrest warrant was issued for all four people involved.Stephen Lynch was arrested in Indiana, Brandon Riggs was already in an Indiana jail on other charges. Annie Riggs was arrested here in San Diego while visiting family for a graduation. Melissa lynch has still not been found.