I have to set this straight: I sailed there from 1967-'73. I haven't sailed in that area since then. I am sure freight traffic is intense by now---it was not a great worry back in the late '60's.
We used to do the race to Encinada every year for about 4 straight, and, out of Newport Beach, to Catalina quite often. No Sea Lions then to harass your transom.
You're welcome. The main reason I tend to think that it was a ramming and quick sinking is that there was no received mayday call. The guy was experienced and I imagine his navigation and radio equipment were in good repair. Even without good VHF radio reception or transmission, he probably had an EPIRB and life raft. Plus lot of contact with the CG nowadays is done by cell phone.
If the boat was taking on water he would have ample time to contact the CG.
I would imagine that the CG has by now contacted all inbound and outbound ships that were in the area at the time. More information will probably be coming in the next few days.
Other options are, of course, as you say. He may not have gone to the Farallons at all. He may be holed up in an anchorage on the bay somewhere and just doesn't feel like talkin'.