How do I (re)mount missing Firewire drives? Why do they vanish?
I can't see a way to change the OS directly, but here's how you would mitigate it:


set up a script to parse diskutil list and possible diskutil cs list and have it mount any volumes that are connected and unmounted
use a tool like Launch Control or Lingon to wrap that script in a launchd trigger mechanism to call it periodically.