Missoula City police and Missoula County Search and Rescue recovered a KAHR semi-automatic 40-caliber pistol.
The loaded pistol was found near 500 block of Burton Street, in a canal by the Clark Fork River.
The search was centered around a waterway off the Clark Fork River, near West Broadway.
Officers are also looking for a shell casing after a city police officer discharged his weapon in a warning shot, after a man on a bicycle refused to cooperate.
Police believed Joseph Peasley was armed. He was arrested on a probation violation.