Cecilia was last seen in Los Angeles, California on September 20, 1994. Her husband, Alfred Newball, saw her at their apartment on Lassen Street, writing thank-you notes for gifts she'd received at a recent baby shower. When Alfredo came home from work, he saw his wife's car parked in the street instead of in their apartment building's secure parking lot. When he went inside their apartment, Cecilia was gone, as was her son, Rene Perez Jr.. A generic store-bought goodbye card signed simply "Cecilia" was inside Newball's Jeep, and her wedding ring and engagement ring were on the vehicle's passenger seat. Cecilia and Perez have never been seen again. They didn't take any belongings, not even clothes or Perez's eyeglasses.

Alfredo received a letter three days after Cecilia and Perez's disappearances, postmarked Van Nuys, California. Inside the envelope was a goodbye card identical to the one left in Newball's car, and a typewritten letter signed with Cecilia's name. The letter stated that Cecilia had taken up with a doctor named Arturo and she and Perez were moving to Honduras with him. The letter said Arturo was possibly the father of her unborn child. Police don't believe the letter was really from Cecilia. There has been no sign of her or Perez since. Investigators believe Alfredo knows more about his wife and stepson's disappearances than he's disclosed, but he maintains his innocence and says he thinks they left him voluntarily.

Cecilia and Alfredo had been married one year prior to her disappearance. Her friends stated there were no problems in the marriage and they do not believe she would leave without warning. She was on maternity leave from her job as a customer service representative at the time she went missing. Foul play is suspected in Cecilia and Perez's cases.