even a hidden backup might just go.
Thieves: My hidden hard drive has an extremely loose usb connection to it. This 'join' regularly comes apart and falls down behind my desk, even when I'm not touching it, so hopefully when the thieves come it will do the same and not be noticed. Although the way life is, that'll be the one time when it DOESN'T come apart !
Flooding: not at our 600' level
Power: a few years ago one of the three phase cables to this house "came apart" where the cables enter the house and fell acros the 'return' lead. What fun that was. Loud, smelly and showers of sparks. Being Spain the people who connected the house to the street three phase many years ago just twisted the wires together and taped the joins over....hence the other thing one needs as well as backups is a UPS with inbuilt filter.