So I guess it comes down to this, is there anything that could have caused both hard drives to fail simultaneously like that while I was driving (not at startup or shutdown)? Would the same thing happen again to new hard drives?
Yes, and yes.
The NUMBER ONE CAUSE OF HARD DISK PROBLEMS in the Empeg
is the IDE HEADER ON THE MAINBOARD.(sometimes I get weary of reminding people of this).
Most likely, one or more pins from the hard drive header (connector) on the mainboard has lifted from its inadequate factory solder job.
It bounces around, sometimes making contact, sometimes not. Heat can make a difference, as can simply lifting the empeg by its handle.
It needs to be inspected and resoldered down flat again, by somebody competent at soldering without destroying the motherboard pads/traces.
Cheers