I had a similar incident with a tomato I was leaving out to ripen... it still looked perfectly fine, but that's because it was full of noxious gas and rotten liquid. We couldn't find the source of the smell and had concluded it was a dead mouse in the wall, when I noticed a small trickle of fluid under the tomato. My roommate went to pick it up and his fingers punctured right through the skin. He actually shrieked... and then the smell! It was like an instant sewer-bomb. We dashed out the back door, gagging. It took a while to get up the courage to go back in and clean up the mess, and even longer to air out the house.
So, yeah. Another good reason to keep the veggies chilled... if they go rotten, at least they are cold and therefore don't smell as bad!