Monica Lynn Appleton, 29, was last seen on October 13, 1999, in northwest Amarillo near the 100 block of Northeast 9th Avenue. That evening her mother saw her there; Monica appeared frightened, refused to leave with her mother and said she would explain later. She disappeared soon after and was reported missing from the family home in Pampa the following month.

At the time Monica struggled with drug addiction and was involved in prostitution. She had two young children, ages 7 and 10, and had recently divorced. Family and investigators have said her disappearance may be linked to the dangerous lifestyle she was involved in. A man named Ivory Tealer, described in reports as a suspected drug dealer, was questioned and later declined to cooperate; reports say he provided no helpful information. An anonymous caller years later claimed Monica was murdered and her body disposed of at a hog farm, but no evidence has supported that allegation.

The case remains unsolved and investigators continue to seek information. If anyone knew Monica, her associates, or saw her in Amarillo in October 1999, please come forward with what was observed.