Details of Disappearance
Knockel was last seen in Dubuque, Iowa sometime in mid-November 1990; the exact date is unknown. He last had contact with his family on November 12. He was driving his maroon two-door 1981 Mercury Sable or Mercury Zephyr with the Iowa license plate number NBL923 at the time of his disappearance; a photo of it is posted with this case summary.
On November 13, his family thought they saw Knockel's car parked along Route 151, just over the Wisconsin border. Within a few hours of the sighting, the vehicle had disappeared; it has never been recovered.
Knockel didn't show up to celebrate Thanksgiving with his relatives, which is uncharacteristic of him. He has never been heard from again. His family became concerned when he didn't show up for the holiday meal and they went to his house.
His loved ones found his wallet, watch and shoes at his home in the 2100 block of Washington Street, but there was no sign of him or his car. He was reported missing on November 26 after he didn't show up for his job at the Swiss Colony mail-order gift house in Monroe, Wisconsin.
Knockel was unmarried and childless, worked menial jobs, didn't abuse drugs or alcohol and and rarely went out in 1990. His loved ones believe he was abducted and murdered, as they think he would never have left of his own accord.
Police stated Knockel wasn't involved in any high-risk activities and he didn't have any enemies at the time of his disappearance. Authorities think it's possible he went into the Mississippi River, but they're not sure whether his disappearance was accidental, a suicide or a homicide. His case remains unsolved.