This just happened to me on Devils Night!
I was driving down a dark road with a huge hill on one side and train tracks on the other. I usually fly down this road because there is no traffic whatsoever. As I approached the hill part of it, within 10 seconds I hear something hit the truck...F--k! I couldn't stop, nor did I want to fearing I would get hit and not be able to catch anyone in the dark. As I got to where it was lit up another 3 minutes down the road, I see that it was an egg and that it hit the rear passenger window. At the nearest store, I pull over to see if there was any damage. I thought there was going to be a ding but no..Thank God!
I always keep a Micro fibre rag under the rear seat and some liquid wax. I was able to get it off right there and clean the rest at home.
I was told that eggs are not good for paint............Just the skin Lol!