Peggy was last seen in Grove, Oklahoma on January 17, 1998. Her husband, James Lee Sweeten, stated he returned home from a work-related conference to find her gone. He stated she left their wedding rings, along with a note saying she was leaving him for a man she met on the internet. She has never been heard from again. Peggy left behind all her personal belongings, including her car and clothing. James filed for divorce three weeks after Peggy went missing, and the divorce was granted in April. He remarried late that year.

The couple's adult son, Patrick, had last spoken to his mother in December 1997. James didn't tell Patrick that Peggy was missing until March 1998, and it wasn't until June that Patrick convinced his father to file a missing persons report. Patrick doesn't believe his father's story about Peggy's disappearance and believes James may have harmed his mother; he stated Peggy didn't use the internet, didn't have an email address and could not have met anyone through there. James was having an affair with a married woman at the time of Peggy's disappearance. The woman divorced her husband in April 1998. She and James moved in together in June and married in December.

Authorities believe Peggy was a homicide victim and James is considered a person of interest in her presumed death. They searched his property in September 2011, but didn't find any evidence there. Her case remains unsolved.