Help on Passport seizure and citizenship issue

Hello, My passport was seized at Kolkata airport while travelling to Canada stating the reason that my citizenship of India is doubtful and I am a Bangladeshi citizen. My parents are citizen of Bangladesh. They sent me to India when I was 12 years old and since then I have been living in India like a Indian citizen for the last 25 years with all Indian documents like Voter Card, Aadhar Card & passport. Immigration officer also noted that I have a Look Out Circular (LOC) issued under my name. They mentioned that they will forward my passport to the RPO Kolkata and I will have to talk to the RPO office. I did talk to the RPO office and they said that till date they did not receive my seized passport. I am working in Canada and if I do not return and join my job there then I will loose my job. Under this circumstances, my questions are: 1. Is there any legal procedure which I can use to go abroad with seized passport/ new passport or any other travel document? Can you please help me in this case? 2. How do I fight to get back my seized passport? Did you handle similar cases in the recent past?