2007 Nissan Versa Hatchback bumping sound

[billpat]

Does anyone have this problem? This just started about 2 months ago. When we drive on a bumpy road there is a clunking sound coming from the back left part of the car. It has been to 2 different dealerships and an independent mechanic no one can figure out what this is. It almost sound like there is a part of a playmate cooler lodged between the frame and the plastic molding. Everything has been taken out of the back including the tire and jack still can't find out what this is. Any ideas out there??? This can be very loud and is driving us crazy!!