Carol was last seen at her residence in the vicinity of west Elm Street and north Hudson Avenue Sturgeon Bay, Wisconsin at 8:00 a.m. on September 8, 1975. Her husband, Richard Pierce, stated he had had coffee with her that morning, then left for work. When he returned home between 4:00 and 4:30 p.m., she was gone. Carol left behind her purse, pet cat, makeup and other belongings at her home. She and Richard had only one vehicle between them, and he had it when she disappeared.

Carol was a housewife at the time of her disappearance and did not work outside the home. Her loved ones described her as a homebody who enjoyed gardening in 1975. Richard was a crewman on the United States Coast Guard cutter Mesquite. He reported her as a missing person on September 15. Prior to Carol's going missing, the Pierces had had plans to move to Cheboygan, Michigan, where they owned some property, on Richard's retirement. Richard did retire and move there as planned later in September, and he still lives there. He obtained a divorce from Carol in 1977 and remarried a short time later.

Carol and Richard's relationship was troubled and they'd been in marriage counseling. Just prior to her disappearance, Carol signed over to Richard her interest in titles to their truck and the mobile home. He said she did this after she threatened to leave him, but Carol's friends and family stated she was happy in her marriage and had no plans to leave Richard. A grand jury investigated Carol's case in 1988, but didn't issue any indictments. In 2008, police searched Richard's farm near Cheboygan, looking for Carol's body, but the search didn't uncover any evidence. Carol's passport and Social Security number have not been used since 1975. Her case remains unsolved.