you were lucky. same thing happened to me when i was out with my girlfriend and two of her female friends, only i couldn't hold it. my girlfriend told her friend to pull over. it was a countryside road, but there was a railing and no real place to hide (like bushes, etc.). to make a long story short, i basically had to pee along side the road out in the open. to make matters worse, my girlfriend had her friends get out of the car to go and watch me (i had been teasing her about her complaining about needing to pee on the way; she made it though). so i standing there with my dick out and her two girlfriends get out of the car and watch me. i still get teased about it six months later.
I would bet ya those girls where dying to be able to grab your dick and aim it all about while it was alive and squirting. Of course they must of done their best to hide how turned on they were watching you. I know this because I've had two girls in the past couple years admit to penis envy.