Small Aircraft; High Wing; 1 Eng; Retractable Gear
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 7.8
Distraction; Situational Awareness
Conflict NMAC
ATC Equipment / Nav Facility / Buildings; Airspace Structure
Aircraft X called on ground at RIW looking for an IFR clearance to ZZZ. Advised aircraft that there was no flight plan on file but would file it for him. Aircraft X gave the flight info; requested routing; requested altitude; etc. I then issued Aircraft X an IFR clearance. In the area of RIW there is poor to no radar coverage below 12000 ft MSL. Aircraft X checked on after departure climbing to 16000 ft. Because Aircraft X was ADSB equipped I was able to radar identify the aircraft out of 7000 and went on with other duties. A couple minutes later; the pilot of Aircraft X broadcast that he had just had a near miss with another aircraft about 500 ft from him. There were no other targets in the area due to the lack of radar coverage so there was no way to call any traffic to him. Aircraft X happened to be on my scope because he has ADSB onboard.
ZLC Center Controller reported that an aircraft reported a NMAC with another aircraft in an area of poor radar coverage.