Mike, you're right, automatics were relatively new, and many people already had made the mistake of hitting the starter with the car in gear. Self-teaching experience, and hope the price isn't injury or a busted bumper and grille.
But your mention of going from a stick to an auto rings true. I always had manual trans cars, and in college, drove a '31 Ford and a '55 Hudson Metropolitan, the latter having 3 on the tree. I had been driving the Met toward the end of my second year, when a friend asked me to keep his car for the summer at my house because School wouldn't let him park it there. It was a big, white '60 Cadillac SDV, stock with a Hydramatic trans.
So I picked it up at school. I'd been mostly driving the Met, but I had to get this Cadillac home, and I was rolling up to a red light, slowing down. But the light turned green, with me slowing from about 35-25. Momentum being at a premium in both the cars I owned, second nature told me to pull the shifter down and into 3rd:
Well, the old girl didn't like that at all, but obediently tried to start to slow herself down to go backward, as I had requested. It shuddered and shook, and took me down to about 5 mph before stalling out. I threw her in neutral, started it up, and purred the rest of the way home.