I still want to know how the bank knew about his bitcoin transactions. Did you explicitly mention bitcoin in the TXN remarks?
I am sure he traded at some Indian (non-P2P) Exchange. It is not difficult for banks to find out the current a/c no. of Indian Crypto Exchanges and then find list of all the customer IDs who transacted with that a/c no.
I am interested to know, those who are facing bank inquiries, did u use savings a/c or current a/c for trading?