When you are looking for a dog there are a couple of basice things - one - while you can mention the breed - lots of folks don't know it so describe the dog (I remember a humane society called me once to evaluate a basenji that was loosing a lot of hair - big time shedding - I went there they had already adopted it out and at it was a Shiba Inu at which point they looked at each other and said - oops I bet it belonged to the people who called.)
You need to include universities and medical labs who do research. I druggie can make 1500 a week stealing and reselling dogs and that's in MN - can't imagine in CA.
If you can figure out what direction the dog went - go 10miles straight line in that direction and flyer that way. If you think he's been at the park and someone picked him up - circle around the park several blocks in each direction, flyer at any school or church nearby and any grooming, vet or pet supply. Check out dog parks in that radius.
I will tell you that I spent a summer in Mt Vernon IL looking for a lost collie - we spent thousands of dollars, and lots of man hours - cable tv we were on the radio etc. Never did find her until after a batcher sold her to another state for purposes of puppies. Then we found out who had her the whole time we were looking.
be sure to add - no questions asked. Another thing we did to increase visibility was to make t-shirts with the dog pix on the BACK with big letters LOST dog on the back. We made several and whenever someone came in from out of state to help us look they had a shirt to wear. Good luck.