Hello and welcome to JustAnswer. Please note: This is general information for educational purposes only and is not legal advice. No specific course of action is proposed herein, and no attorney-client relationship or privilege is formed by speaking to an expert on this site. By continuing, you confirm that you understand and agree to these terms.
I am sorry to hear about this situation. If the parent whose custody is being challenged does not show up to Court, the Court may rule in the other party's (your father's) favor automatically by default. As such, one wants to show up for any hearing the Court may have scheduled, and generally wants to reply to any pleading. Simply ignoring the situation is not going to make it go away, I am afraid - it may only hand him an easy "victory" in Court.
Finally, using counsel is recommended, but not mandatory. Let me know if you need leads for pro bono/low cost counsel in CA.
Please note: If I tell you simply what you wish to hear, this would be unfair to you. I need to be honest with you and sometimes this means providing information that is not optimal. Negative ratings are reserved for experts who are rude or for erroneous information. Please rate me on the quality of my information; do not punish me for my honesty.
I hope this helps and clarifies. Please use the SEND or REPLY button to keep chatting, or please RATE when finished. You may always ask follow ups at no charge after rating. Kindly rate my answer as one of TOP THREE FACES/STARS and then SUBMIT, as this is how experts get credit for our time. Rating my answer the bottom two faces/stars (or failing to submit the rating) does not give me credit and reflects poorly on me, even if my answer is correct. I work very hard to formulate an informative and honest answer for you; please reciprocate my good faith with a positive rating.