Miller was last seen jogging at 10:00 a.m. on August 16, 1983 in her hometown of Idaho Springs, Colorado. She was last seen in a park near her family's residence. Investigators believe that a male seen in the park at the same time as Miller may have been seen speaking to her. The man was driving a small red 1975 or 1976 pickup truck with a white camper shell and out-of-state license plates. It has not been established if the man has any connection to Miller's disappearance, but police are interested in identifying him and questioning him. Miller's sister says a man in a red pickup truck had flirted with Miller a few days before she vanished, but the sister could not identify the man or remember very much about him or his vehicle; it is unknown whether it was the same person seen nearby when Miller vanished.

Miller disappeared shortly thereafter and has not been seen again. She did not have any cash or personal belongings with her on the day she vanished. Miller normally left a note for her parents if she was going away for any length of time; she did not do so on the day of her disappearance. Miller was a basketball player in 1983 and she jogged regularly to stay in shape. She is one of seven children. At the time of her disappearance, she baby-sat to earn spending money; her baby-sitting earnings were left behind at her house when she vanished.

An unidentified Ohio man has been under investigation for several years in Miller's case. Authorities believe he may have been involved in Miller's presumed abduction, but he has never been charged. In 1995, a serial killer from Mississippi claimed that he had killed Miller, but police did not find his story credible. Another suspect, a New Mexico man named Edward Apodaca, is deceased; he was murdered by his wife and mother-in-law in 1990. Apodaca's former girlfriend claimed she had helped him bury Miller in the mountains near Idaho Springs. Three cadaver dogs indicated the presence of human remains in the place the girlfriend indicated, but police excavations turned up no evidence. Miller's family believes, however, that Apodaca was in a fact involved in Miller's case.

In 1994, a missing children's hotline received a bizarre anonymous call about Miller's case. The caller stated that he or she had seen Miller together with Tiffany Sessions and Tracy Kroh and that the three young women were being held against their will in Austin, Texas and forced to work as prostitutes. Sessions and Kroh both disappeared in 1989, Sessions from Florida and Kroh from Pennsylvania, and no one had suggested the cases were related. The tipster claimed the three women were being held by a man named Thomas Stewart and traveling in a white van with Florida license plates and a blue/gray van with unknown license plates. Police from all three states investigated the tip but decided it was probably a hoax. In 1995, a woman police picked up in Tampa, Florida claimed to be Miller. Miller's parents flew to Florida to meet the woman, but she turned out to be someone else.

Possible evidence relating to Miller's case was found in Empire, Colorado in 1994. Some bone fragments, a piece of fabric similar to canvas, and a single blonde hair was found buried near Interstate 70. The bone fragments have never been identified; police do not even know if they are human. The fabric was very degraded and appeared to have been buried for a long time. In 2004, the police sent the hair to the Federal Bureau of Investigation (FBI) to test for mitochondrial DNA. They hope to conclusively link the hair to Miller's case.

Miller's family had her declared legally deceased in 1994. A grand jury investigated her disappearance in 2007, but the jury disbanded in November of that year without any indictments being handed down. but her case remains open and unsolved.