I think this is how it happened on my car- I recently moved from KS to CO. On the drive out, the trunk and the rest of the Protege was loaded down pretty heavily with "stuff" with caused the rear end to squat. While leaving a construction zone and passing over that BUMP between the construction zone pavement to the existing pavement, my wife (who was driving the Protege) radioes me and says that there is a weird rattling noise coming from the rear. I thought it was just the exhaust rattling on something. And since I just though it was the exhaust, I wasn't too worried about it and drove around for about 3 months before checking into it. At least, that's my best guess as to how it happened. Pretty scarey actually since when I rotated the bar back, I had to be careful to not catch the rubber brake lines on the nut for the end link at the end of the bar.
New parts (new lateral link and MSP end links) should be here tomorrow.