Glenn was reported missing by a neighbor on October 4, 2004, the day after he was last seen. He was supposed to travel from his home in the 14900 block of Airlie Road in rural Polk County, Oregon to Oakland, California to attend a meeting about the sale of an item that has been in probate since his father died in June 2003. There was a disagreement between Glenn and other family members about the estate. The meeting was to be held on October 6; Glenn planned to leave on October 3.

Glenn never arrived at the meeting and has never been heard from again. His loved ones said it would be uncharacteristic of him to miss the appointment. His unlocked truck, which was packed with luggage and travel items and business papers for the trip, was found at his house. His pet cat, which his neighbor was supposed to feed while he was away, was also left behind. That same neighbor reported him missing.

Dale A. Pennie, Glenn's brother, is considered a person of interest in his disappearance. The brothers had been in conflict over a $1.5 million inheritance, which may have played a role in Glenn's case. His daughter inherited the majority of the estate and Dale got only $29,000. Dale denies any involvement in his brother's disappearance. Glenn had been afraid of him and had, in fact, told others that if anything happened to him, Dale should be a suspect.

Investigators consider Glenn's case suspicious, but little evidence is available in his disappearance. He is described as a methodical man; it is uncharacteristic of him to leave without warning. His case remains unsolved.