It could be a rear wheel bearing, mine gave up the ghost last year, but that's after 13 years of ownership. For one to go on a three year old car seems quite unlikely. As you have an "x", I wonder if there's something with the driveline. Do you recall having bottoming out at any time? Also, just to add to your anxiety, "certified" can be a meaningless term concerning used cars, any type, but before worrying about that, getting a diagnosis is in order.