"The citizen had pulled over and recovered it with the intent to return it to the officer right then, but the officer had by then driven off, so [the citizen] kept it because he had an appointment to get to, and then returned it to us last night," Burbank said.
"We of course are very appreciative of him," the chief added, confirming that a $200 reward police had earlier put up for return of the handgun would be offered to the citizen, whose identity was not released.
On Wednesday, the officer, described as a veteran lawman with a good service record, had driven from 700 South and 1050 West, got on Interstate 15 at 400 South and continued on to Woods Cross before realizing the weapon was gone.
Burbank said the officer now faces an investigation by his department's Internal Affairs division.
"They will ask questions, review [the case] and then present it to me to make any decisions on discipline or training required," the chief said.
Burbank said that while he is relieved the weapon was recovered, it remained a serious incident.
"I know the officer is taking a beating in the media. He is a well-qualified officer [who made a mistake]," the chief said. "But we just can't afford to have this happen."
Per departmental policy, the officer's name was not released while the incident is being investigated.