It is possible that your father transferred all of his assets into a trust before he died. That would explain the CPA's statement that he "died with no assets". The assets were owned by the trust. A trust is not a public document and only the trustee and beneficiaries have knowledge of what is in it. You will not be able to find the assets of the trust without the trustee's cooperation.

I don't know what a "special trustee for an estate" is. A trust and an estate are two separate entities. They exist independently. The family corporation should be registered with the CA Secretary of State's office, but there is no public record of its assets. If you are not a shareholder in the corporation, you would not be entitled to information about its assets. You didn't say how long ago your father died. If it has been a while, i.e. a number of months ago, and you haven't received a notice of probate or any notification from the trustee that you are a beneficiary of the trust, then in all likelihood you were not named either in a will or a trust.

I have answered your question. Please click on a 3,4,or 5 rating so that I will be compensated. If you are not satisfied with this answer, please send me a Reply with what you feel is wrong with the answer and what additional information you are seeking.
Clicking on number 1 or 2 is not necessary in order for me to explain my Answer. BONUSES for quick and helpful responses are very appreciated. If you have additional questions, I would be happy to assist, but as a courtesy I respectfully XX XXXXXXXX rating for the original question before you branch off into other new questions.
Also, this answer does not create an attorney client relationship and you are urged to consult a local attorney to verify the accuracy of this answer according to your state's laws and local customs and practice.