My MacBook Pro got stolen, and I have file vault enabled but not the Firmware password, too strange on Apple's part not to set it on by default when you set a user password or at least to raise awareness about it. I'm an advanced user but never thought about the firmware password.
Anyway, my biggest fear now is that the thief can erase the disk using recovery mode, reinstall macOS and have a new apple id configured, allowing him to bypass the "find my iPhone" notification and lock.
Is that doable? If so, that redeems the whole anti-theft features of "find my" worthless!