I'm sorry he scared you, but I seriouslly LOL'd at your DH driving off with his truck still plugged in! My DH drives a diesel also and I could totally see him doing this!!
He said "you need to remind me to unplug it."
ummm.. So YOU want ME to remind you to plug it in and unplug it?
I'm thinking today I make a big sign to stick on the garage door that says "TODD, Plug & Unplug truck. You're welcome. Love, The Wife"
Maybe it will embarrass him enough to have all the neighbors see it he will remember on his own.