If you do not believe there was ever a formal order, you may want to get a copy of the file from the San Diego court case, but you will want to contact DCSS in Ontario and speak with them immediately. It is important to keep in communication with DCSS when trying to sort things out.
Also, you may want to speak with a local attorney to determine what your choices would be, because someone is claiming that this is your child. Without specifics on the details of your case, you may or may not have any recourse against this.
Phong H. Han
Eaton & Associates
707 18th Street
Bakersfield, CA 93301
This answer does not create an attorney/client relationship and is not to be construed as advice for a specific issue. The answer given is a general response to general areas of law that may or may not apply to your case. To have a more specific answer to your set of facts, it is always recommended that you speak to an attorney in your area.