by taking the car for an estimate to the local place where bmws get farmed out for collision repair. it isn't much, but the guy was certain enough after seeing the minor gap in the bumper to include a bumper absorber in the estimate straight away, and note that the estimate was "open". i wasn't really looking for much from the original adjuster, but when he was insistent that the bumper would merely have to be taken off and adjusted to proper fit again, i knew that i would have to get a second opinion.