Earlier quoted context omitted.
> There is no reason the keys have to be stored > separately. That is orthogonal to the actual requirement > that the private key is private aka. secret. It's effectively required to store the keys separately because if you stored the public key on the key bastion, it would be useless. > In fact, the public key is public meaning it is assumed > that anyone has or could gain access to it. It is > purposefully publishe…
A public key is a file. It can be stored in more than one place. For example, you can generate both inside the key bastion, and then copy the public key to the public servers, while leaving a copy on the bastion.
If they had kept their private key where it belonged, we wouldn't be having this discussion because their security alert would have said "...and we have verified that no credit card data was accessed".