My sister kidnapped my dad from Boston to California. I will have to file for guardianship. Has anyone been thru this process?

HELP. I have a sister who arrived unannounced on a Monday night thinking I was at my grandson’s birthday. She mentioned taking him to Hawaii for a few weeks. She started screaming at me because her last visit in May, she showed up unannounced and tried taking over the stocks, his wallet went missing, told the bank she was his lawyer and tried having me removed as POA. I have lived with him 10 years and he has shown cognitive decline since 2016. I went to the police and filed a report for the missing wallet. She told the police he was going on a vacation and she was just visiting for a few days. I went downstairs and he was gone. She did not take his cane or walker but took all the checkbooks. His Passport and accounting books. I have called APS in both California and Boston, talked to a social worker, his doctor and nurse. I have tried several lawyers. I thought the elder attorney we paid $5,500 covered these issues. One only did a will and trust. Another wanted a retainer of $7,500. I am in Boston so it takes couple days for people to get in touch with you. The police called her last Saturday and she stated that he lives with her every winter. He has never lived with her. Her husband called me a psycho bitch and said George lived with us last winter. They will not let me speak with my father. The nurse said he sounded happy and when she asked him if he was spending the winter there he said no. My sister then started screaming, "Yes he is spending the winter here!" I did a wellness check last week. I am still trying to get a Lawyer I feel comfortable with. I will have to file for guardianship. I have lived with him for 10 years. He visited her twice in 13 years for a week because I asked her to give me a break.