Martinez was last seen at 12:00 p.m. on July 6, 2004, when she was dropped off at the Krug Pool in the vicinity of St. Joseph Avenue and Krug Park in Saint Joseph, Missouri with her younger brother. When her mother came to get them later, only the brother was waiting; Martinez had disappeared.

Subsequent investigation showed that Martinez had planned to run away to California with Christopher M. Hart, a 32-year-old living close to her home. He was on parole for second-degree assault and has also been convicted of drug possession, unlawful use of a weapon and resisting arrest. He and Martinez were reportedly going to go to California.

Eleven days after Martinez's disappearance, Hart was arrested in Olympia, Washington for purse-snatching. He gave the Washington officials a false name and as a result they did not know he was wanted in Missouri, so he was released. On September 7, two months after Martinez's disappearance, Hart was arrested again after Washington police discovered his true identity and the charges against him in Missouri. He had been staying with a cousin in the Olympia area.

Washington investigators found no sign of Martinez, or the stolen gray 1995 Pontiac Bonneville with Missouri license plates numbered 377MPY, which she and Hart had allegedly been traveling in. Hart's cousin said he had not seen Martinez or ever heard Hart mention her. Hart, who remains in custody, has refused to divulge any information whatsoever on Martinez's whereabouts. He began acting bizarrely while in jail and was sent to the state mental hospital for a psychiatric evaluation.

Martinez may still be in the local area or she may be in the Kansas City, Missouri area. There is no evidence that she ever arrived in Washington. When she disappeared, she left behind all her personal belongings, including her medication and her three cats. Martinez ran away from home once before, in 2001, but she did not leave the state and was only gone for about a day before returning home voluntarily. She was an eighth-grader at Robidoux Middle School at the time of her disappearance. Martinez's case remains unsolved and is still classified as a runaway.