Rear Suspension Coil Springs problems of the 2009 Chevrolet Traverse

The passenger side rear coil spring broke. This happened while sitting still in traffic, I heard an loud noise --- like a fastener breaking and then vehicle rocked. I pulled over very shortly and checked to see if a lug nuts or tire blew and didn't see anything unusual. I just had my tires rotated (4-2-14 ) at local shop and told them about the incident and they found the top part of coil spring -- approx. 3 to 4 inches had broken off. I got an est to repair and was told that their parts supplier had over 150 units of these springs in stock. ( very unusual to have this many pcs in stock unless there are problems w/ it ) I also then went home and checked on internet and there are lots of GMC & chevy veh's of this type that are having similar problems / issues w/ the coil spring breaking. I checked to see if any recall or advisory was listed -- nothing. This is something that should not be happening -- I drive may road miles and there certainly is no abuse to this veh. I now may be stuck w/ a $ 300. 00 plus repair bill which is not something I'm looking to do because it's recommended that both coil springs be replaced because with only putting on 1 it will be stiffer than the one on drivers side and most likely it will break also because of the shift in weight from the new one. My next concern -- if driving on the interstate or any road for that matter and the coil spring breaks and it causes my tire to be damaged it could be the cause of an accident or maybe it has already been the cause and not yet discovered !!!!!.