Philip's masters degree was in urban planning and he could have skimmed the Land Use document for Pleasanton Ridge and headed north in the direction of the house that is the EBRPD security/maintenance in the north portion of the park to get help on purpose. Also he may have headed toward the Emergency Vehicle Access point in the north part of the park intentionally. He may also have thought Devany Canyon's entrance/exit had been opened. If you look at this short document, you can see why
https://www.ebparks.org/civicax/filebank/blobdload.aspx?blobid=28136 On p. 2 it says "NEW – Devany Canyon Walk-bike access – No vehicle parking" He was found really close to this.
One thought that I think is possible that he did not want to return via the "Lying Stump Shortcut Trail" that is found on Strava as well as some biking websites because he could have thought it was a really horrific and steep trail and wanted another way out. I can't reference some of the web comments that begin on the one that starts with an r but some people who retraced the route said that portion was horrible and it took 2 1/2 hours to do that route particularly because the first 2 miles was awful.
Philip stayed on the main Fire Road called the North Ridge trail until it seemed to just end at the top of the hill at 11025 Dublin Canyon Rd, the address where EBRPD has a residence called the Poole house where an EBRPD maintenance supervisor lives. It could be that he knew about the house since it appears in the Land Use documents and on purpose headed in the direction of the house.