On the Find Richard Moss FB page, his father posted something of great interest.Here's my summary of one part of the search:
https://www.facebook.com/groups/1799357063726732/
They searched a ravine south of Caltrans Ravine, which is separated by a mountain. There is apparently a broken 4" wooden signpost at the north end. They think the break is caused by an "impact". The ravine is noted an impenetrable because the thicket is ranges from 3 feet tall to 15 feet tall at the bottom of the ravine. I guess there is also a dry creek bed at the bottom area, and I'm guessing when it's flowing with water it just feeds the thicket and stinging netties and makes it more dense. I guess those stinging netties are really mean right now, and hindered searching deep into the thicket. Maybe they need a machete. In conclusion, they were unable to fully search the ravine, and only did a visual search from the southern rim road and 350' up from the north mountain.
They are sending a drone out today to see if they can see anything there. I hope SAR can also get in there and check it out more thoroughly. If he is in there, he could still be alive but unable to open the car doors due to the thick brush, or not able to exit the vehicle due to the stinigng netties.