labor started with little to no signs or labor?

i have a friend who went into labor and had no idea she was in labor. she said her contractions at their strongest felt like back aches but they were very tolerable. her water didn't break until   after she got to the hospital but she was already 6cm dilated by then. labored for 1 hour after that and baby basically fell out with one push. 😳 has anybody had something similar happen??! her story scared ts out of me. I'm hoping that's just a super rare and random thing lol