If you found the phone number from an internet resource it may be outdated information. Have you tried writing a letter to see if you have the current address? Under your return address you might add "Postal Service Requested" and use a yellow marker for this note. That way if she has moved the Post Office will send you the address where they forwarded the letter (if she moved within the past year).
California Search Website:
Other great websites to check out:
http://www.adoptionchat.com
http://www.adoptionlists.com
http://www.adoption.com
http://www.adopting.org
http://registry.adoption.com/