Thats interesting, that your wheel bearing went bad and you did not notice. Had you ever checked to see if there was any play along the plane of your rear axle? In my experience, as the bearings go bad, a small amount of play develops along the horizental plane of the axle; if you grab the wheel at two places (hands across from each other) and try to move the wheel, the plan, if its there, will be obvious. Checking the bearings and re-greasing once a year is a good idea as well.