If someone scammed me in Bitcoin in Pakistan, should I report it to the police or FIA—especially if Bitcoin is illegal?

Bitcoin is not illegal in Pakistan (at the time of writing this answer). There is no entry in the Pakistan Penal Code (PPC) that makes it so. What State Bank of Pakistan has recently said that the institutions that SBP licenses and regulates are barred from dealing in crypto currencies, bitcoin, ICOs, etc.

Your recourse is under section PPC 420 (defrauding another person). What you will have to prove is that there was an asset value assigned which you were swindled out of.