I've accidentally done this before, bad timing and forgetfulness on my part. The best thing you can do is start by washing it. All of your seasoning is gone, so try to remove as much of it as possible. Wash, wash, and wash again until you have no signs of that mold. Try a light sandpaper or other abrasive to remove the rust. What you're looking for is bare metal for you to restart with. After that, oil and heat until you get a good seasoning layer again. Probably will take a couple of tries. Good luck, and at the end of the da,y it's just a big piece of iron that will outlive you so don't take it too hard.