Hoping for details as to where he was found, why he would go off trail on to a game trail (which is so different from a running trail) and what his friends think happened.
Unless the law enforcement agencies are able to get his watch up and running and follow where he went and when, I am not sure we will know what happened.
What I have heard are some possibilities are:
Scenario 1: He made it to the loop trail on Pleasanton Ridge and completed it and could not get back to Moller Ranch----If he had not been able to climb the gate back to the Moller Ranch area via that side northeast heading "Lying Stump Shortcut trail," he would have had no choice but to continue north on the North Ridge trail. If you look here, you can see it leads to the darker shade green which indicates the landbank area---(zoom into see this in more detail)
https://www.ebparks.org/civicax/filebank/blobdload.aspx?BlobID=29796
In the area where he was found, there are 4 wheel drive and single track trails, none of which probably have any signs because it is in the landbank area. The area where he was found is near the two red dots, one of which is the Poole house EBRPD security residence, the label water tank, etc. Perhaps he was trying to get out via Devany Canyon toward I-580 and did not make it.
Scenario 2: He got lost on the way up to the top of Pleasanton Ridge, made some wrong turns on the "Lying Stump Shortcut trail" and ended up in landbank area next to the adjacent neighborhood, the Preserve.
Scenario 3: He turned around in Moller Ranch because the trails were in such poor condition (mountain bike ruts, too steep, compacted uneven dirt), went to the Preserve trails, and tried to access Pleasanton Ridge from there, but never made it.
Scenario 4: Possibly Philip found this EBRPD concept map of trails on the internet
https://www.ebparks.org/civicax/filebank/blobdload.aspx?blobid=26896 did not realize this was a concept map and did not scroll down to see this is a trails map for trails, some of which do not exist yet or do exist but have no signs. He assumed these were the trails and went north toward the Devany Canyon area near the top of the map and tried to exit the park through Devany Canyon.
Scenario 5: Philip used the noise from the freeways to figure out how to get out of the park, but unfortunately did not make it.
Hopefully the law enforcement personnel will retrieve the data from the watch to figure out and retrace his exact path he took. Until they do, I think anything we say is speculative. I don't know whether they plan to download and analyze the watch data, but I hope they do.
p.s. I am basing the location he was found on the SF Chron map yesterday and thus think he was found on the Poole property in the landbank EBRPD property. If I see a more detailed map that is different than the SF Chron map, I'll relook at the Pleasanton Ridge map I have with parcel data and correct it.
