It was UA on a 737-500. I never flew it, but remember it coming up when searching for fares to YYC. This was in the early to mid 90s, IIRC. It may have been a tag from SFO or DEN.
Yeah, it was probably an enroute stop...BOI, a similar sized market, has multiple flights to SFO a day on UAX so I'm suprised GEG doesn't have at least a CRJ-200 heading up there, my guess is that it would be packed...both WN and AS fly between BOI and GEG so it would make some sense if the UAX Boise flights went on to GEG...just a thought