Curt,
I'm so sorry that happened to you, but very happy it wasn't worse.
I worry about that all the time. I'm almost OCD about it--checking that the coffee maker, dryer, etc are off when I leave the house. I've even driven the 20+ miles back home from work a couple of times because I'm afraid I forgot to turn something off.
I'm hoping Scooterman will chime in here and shed some light on what might have happened.
When I wired my system, I put a GFI box under the tank and all of the power strips are plugged into each other in series then into the GFI, which in turn is plugged into a GFI curcuit in the wall. Probably overkill. I knocked a VHO bulb into the water once and the GFI under the tank kicked off, so I feel it works properly. I also use a metal-cased strip--don't know if it's better or not.
I am going to buy a smoke detector today.