On David Paulides' latest Missing 411 YouTube video, he goes over a missing climber story from 1972 in Mt. Jefferson.
At ~ 52 minutes in the link below, Paulides tells the story of Steve Stokeley (the 19 year old man who went missing after summiting Mt. Jefferson).
Apparently, Steve was more aggressive and/or better trained than his 3 friends and wanted to climb the summit via a harder but faster route. He made it to the top solo and before his 3 friends.
According to Paulides, Steve was coming down from the summit and told his 3 friends (who were still climbing up) that he will meet them down in camp.
Steve never made it to camp and his body was never found.
What Paulides does not explain is that climbing Mt. Jefferson is not a piece of cake and is very dangerous (you need crampons, ice-ace, and rappelling skills).
Below are links to a couple of videos of climbers summiting Mt. Jefferson and they show how difficult and dangerous that climb is.
https://www.youtube.com/watch?v=mfrkes4HuT0
https://www.youtube.com/watch?v=ISFS0zAyCBE
After watching these 2 climbing videos, I concluded that that climb is treacherous and a bad move above the red saddle could lead to a fall to death (thousands of feed down).
Just this year, a guy fell to his death but his body was found 3 days later via helicopter search (see link below).
https://ktvz.com/news/accidents-crashes/2022/07/05/fallen-climbers-body-recovered-from-slopes-of-mount-jefferson-privately-funded-helicopter-helps-in-effort/
I don't think there is anything anomalous about this missing person case. Mt. Jefferson has several glaciers north and east of the peak; and if Steve fell into one, it could take years to find his body. Very sad story nonetheless.