Pedro was last seen on the morning of September 13, 1982, when she was dropped off at school in Atwater, California. When her mother went to pick her up at 1:30 p.m. that day, Pedro was nowhere to be found. Her mother waited half an hour, then asked the school to page her. She waited another half-hour, but Pedro did not respond to the page, so her mother contacted Pedro's father. They waited for her until 4:30 p.m., then went to the police. Authorities refused to accept a missing persons report until 24 hours had passed. Pedro has never been heard from again.

Pedro was a senior at Atwater High School in 1982, and was planning to graduate early. She was an advanced student and a classical pianist. She also has a black belt in karate and was active in aerobics. While some agencies classify her as a runaway, it is unclear what happened to her. Since her disappearance she has not applied for a driver's license or used her Social Security number. Her father died several years after Pedro went missing and her mother remarried and moved to Oregon. Her mother is still alive and searching for her.

Some agencies may list September 13, 1986 as the date Pedro left her family's home. Some agencies give her date of birth as September 21, 1965. Her hometown may be listed as Merced, California in some reports. That city's police are assisting with the investigation into Pedro's disappearance.