Madison and her friend, Susan Smalley, planned to spend the night of March 19, 1988 at the Smalley family residence in Carrollton, Texas. It has been established that the girls were at the house at approximately 12:00 a.m. on March 20, as Madison called a friend from their home at that time. Smalley and Madison departed together afterwards. They were traveling in Madison's 1967 Mustang convertible. The car had been painted green and gold, the colors of Newman Smith High School, where the girls were students at the time.

Smalley and Madison apparently attempted to purchase beer at a local 7-11 convenience store in the early morning hours of March 20. They were refused service due to their ages. The girls then drove to the Steak and Ale in Carrollton, where Smalley was employed. One of Smalley's co-workers told investigators that Smalley spent approximately five minutes inside the restaurant speaking to a friend, then departed. Madison stayed inside the vehicle while Smalley was in the establishment. This was the last confirmed sighting of the girls.

Smalley's mother called authorities when she noticed that neither of the girls was in the family's home later in the morning. Madison's convertible was located later in a strip mall parking lot in Dallas, Texas on Forest Lane and Webb Chapel Road. The vehicle was locked and appeared to be undisturbed; Madison's portable stereo was placed on the back seat. Foul play is possible in their disappearances. It is believed that they may have been abducted and taken to Mexico.