Actually, I'm wondering how does a bitcoin bank avoid physical robberies? For example, a criminal or government officials physically kidnaps a bank official and

Actually, I'm wondering how does a bitcoin bank avoid physical robberies? For example, a criminal or government officials physically kidnaps a bank official and demands the private keys? How do you implement the equivalent of cryptographic vaults that only trusted officials have access? In addition, how do you track the serial numbers of stolen bitcoins?