re: I left my cast iron outside like an idiot

You didn’t hurt it.

If it’s surface rust, clean it with white vinegar to remove the rust. You can even soak it in the vinegar if it’s bad. Rinse it with soap and water, then just water. Heat it to warm and get it dry. While warm apply a very thin coat of oil (canola or grape seed). Bake at 450 for an hour, turn off oven and leave in oven until cool. You may have to repeat these last steps several times. Now cook cornbread/fry bacon and you’ll be back in business.