Montiero was last seen at her residence in the 1800 block of 7th Avenue in the New York City borough of Manhattan on April 2, 2000. She was speaking to a friend on the telephone at approximately 7:00 p.m. when her boyfriend, Heriberto Palacio, was overheard screaming at her in the background. Montiero has never been heard from again.

Authorities apprehended Palacio in late April 2000 and questioned him regarding Montiero's disappearance. Palacio was convicted of murder before his girlfriend vanished and had since been released from prison. Investigators detained Palacio on unrelated charges while conducting a search for Montiero. Search efforts were concentrated near a section of the Grand Central Parkway in the borough of Queens, but no trace of Montiero was found.

There have been no arrests in Montiero's case; it remains unsolved. Montiero and Palacio's relationship was apparently troubled at the time of her disappearance. They have a young child together.