If someone steals your money then you need to call the police and make a police report on it.
If you don't know who stole your money though then there's not much that can be done by the police but making a police report is a good idea anyway.
If someone broke into your house and stole money out of your house then police should be called for the break in as well.
If someone gets into your bank account and steals your money then making a police report is needed as well and then contact the bank.
Sadly though if someone hacked into your bank account or had access to your bank account and stole money from your bank account then you likely will never get that money back.
The banks will not pay back the stolen money because the FDIC insurance is only for if the bank goes under and not if someone gets into your bank account unless it was the banks fault that someone got into your bank account.
If you're not sure who stole your money you're sadly likely to never get it back unless you know who did it.