On what frequency? Guard? The folks above would generally be on another, usually unpublished, frequency.
Usually, when you lose contact with ATC, you can hear one-sided conversations. Other aircraft need not be above, but can be in a better location. For instance, flying around Carquinez Bridge below 2500 or so, you'll lose contact with NorCal. You'll still have contact with anyone over San Pablo Bay to the south, pretty much anywhere around Mt Diablo (except directly behind it), and probably the north shelf of Oakland's Class C. SOMEone will hear you.
To get to the "unpublished" frequencies, you need to be over 10,000 MSL locally -- for instance, over the top of the Class B. Center frequencies are generally published on IFR charts, but Approach only is for B and C transitions.
And Approach/Center is only going to freak out if they also lose you on radar. If they can see you're merrily flying along and not descending, they won't think you crashed. If, on the other hand, you stop talking to them and disappear off radar (such as, when you land somewhere), they will not be comfortable with that. Now, searching doesn't mean they immediately wake us up. They try other stuff first. Like asking other aircraft in the area to relay messages. Maybe phoning nearby towers to ask if you're there. Calling the FBO at your destination. And so on.
You can also try going back to your previous frequency. Sometimes they can still hear you.
You can use Guard if nothing else works. You might reach a DIFFERENT ATC facility. Like, at Carquinez, you could probably reach Napa, Concord, or Travis towers. Or any of the local aircraft that might be monitoring like they should. Some of us actually do that.
