Jonelle Matthews had just performed at a holiday concert in 1984 with her middle school's honor choir in Greeley, Colorado, when the 12-year-old girl was dropped off at her home by a friend and the friend's father. The seventh grader was never seen again. But on Tuesday, her remains were found, the Greeley Tribune reports. Police reopened the missing persons case last year, reviewing old interviews as well as conducting new ones and asking the public for help. And on Dec. 20, the 34th anniversary of her disappearance, they released video of the Franklin Middle School concert showing the pre-teen smiling as she sang "Jingle Bells" with her classmates, the AP reports. Oilfield workers digging a pipeline at an oil and gas site in rural Weld County found bones Tuesday, and on Thursday authorities announced they had been identified. (More missing child stories.)