Camping is probably the wrong word here, since you are unlikely to be camping a lot during your vol bivouac. And if you are, then certainly not on a camping site. Not that camping sites are expensive (Come on! Get real! Only slightly more than twenty euros for a noisy place with stinking toilets, lukewarm douches (possibly requiring a slight additional payment only), screaming children, barking dogs, arguing parents, fighting neighbours, shouting radios and televisions, wildfires disguising as barbecues, and drunken adolescents beating the same chord on a de-tuned guitar over and over again until 4h38 in the morning, is a bargain in comparison with a frightfully quiet night out in the open under those scary stars and moon.), but the title 'Surviving a cold rainy night in the mountains without a tent and sleeping bag, while the wind and wolves howl around you' was just a tad too long for this page.
What your are probably looking for is the word bivouac.