Montague was last seen leaving a friend's home in the area of 8400 West and 3500 South in Salt Lake County, Utah at approximately 3:00 a.m. on September 22, 2007. She was driving her husband's silver or pewter-colored 2002 Chevrolet Trailblazer with the Utah license plate number 215LTE at the time of her disappearance. Montague's friend followed her back to her own residence, and saw Montague pull into the driveway, then pull back out. As Montague did this, she hit a chain-link fence and damaged it. Montague never arrived home and has never been heard from again. Her vehicle has not been recovered. It will probably have damage on the driver's side rear and possibly the whole driver's side. She had been drinking alcohol on the night of her disappearance, but it's unclear whether she was intoxicated.

There has been no activity on Montague's financial accounts since her disappearance, and she has not renewed any of her prescriptions. Authorities do not suspect foul play was involved in her case, but her family stated it is uncharacteristic of her to leave without warning and they fear for her safety. Montague had custody of her three grandchildren at the time she went missing. Her youngest son died in 2009, two years after her disappearance. Her case remains unsolved.