I was called out to a new house (3 yrs old) to check out some problems the owner was having with his electronic equipment for the Home Theater. I didn't find anything wrong with the circuit (polarity, loose neutral, etc.). However, when I went under the house I found a #4 stranded ground wire with a pipe clamp just lying there on the ground. I wasn't sure if this was for the water bond or ufer. I checked the panel (200 Amp) and there was no other grounding/bonding wires on the neutral bar besides the #4 that went under the house. I checked the line side of the panel to see if they landed in that space but there was nothing.
I crawled around the house checking on top of the stem wall for a ufer but found none. I figured the electrician/concrete guy forgot to put one in and the electrician just threw the wire under the house and hooked it to the panel to fool the inspector. So, I'm guessing this may have something to do with the electronics issue. Yes? Is there a possibility of physical harm to people in the home?
Additional observations:
1. The water main stubs up with PVC so using that as a GEC won't work. The water does stub into the house with copper but I think most of the plumbing is plastic. Do we still need to bond the water just before it goes into the house? My guess is yes.
2. There is no gas bond at the meter or hot water heater. How important is this for safety? I know it is a AHJ call.

Location of home is Sacramento, CA.

Many thanks,
Byron