Sondra was last seen at her family's residence in Santa Fe, Texas on October 26, 1983. She disappeared from their house and has not been seen again. The door to the home was open and biscuits were baking in the oven at the time Sondra vanished. Her coat and purse were also located inside the residence. She was initially believed to have gone to the store for a moment, but she never returned to the house. Some reports may state that Sondra disappeared while en route to school during the morning hours.

Sondra's father reported her as a missing person during the following morning. Authorities initially classified her as a runaway, but the circumstances surrounding her disappearance are unclear. Several investigators believe Sondra may have started a new life for herself with an assumed identity, but there is little evidence available in her case.

Sondra's case may be related to a string of disappearances and/or murders of young women from the Galveston County, Texas area since the 1970's. Michelle Thomas vanished in 1985, Suzanne Richerson disappeared in 1988 and Jessica Cain vanished in 1997. Law enforcement has not determined if these four cases are connected.