I'd consider the Mist Train hiking, even though about 2/3 of the way is paved, and I've seen people do it in normal running shoes.
This is the description of the trail that he hiked. But right now there's a good deal of snow and we've had some pretty bad weather the previous week. He seemed rather adventurous to do this in those conditions. I think I've done something similar in Yosemite in winter.
Mt. Baldy Trail
Area Status: Open
The Mt. Baldy Trail is 6.4 miles long. It begins at Mt. Baldy Village and ends at Mt. Baldy Summit. The trail is open for the following uses: Hiking
The other thing is that his cell phone location has been triangulated and he was moving before it stopped - likely from the battery dying. If I go almost anywhere now, I carry multiple USB power packs. I think my biggest one (and it's heavy like a brick) could probably power my phone for about 5 days of just being on without doing much else. But that might be enough to locate me if I was being looked for.
I'm not sure why he didn't call someone.