30km/h is a relatively low speed impact (its about 18mph). Since BMWs have a pretty strong bumper (unlike Toyota bumpers......), you can see that the bumper and the honeycomb-like absorbing structure underneath did its job.

Note to the OP: make sure there is a thorough inspection of the structure. While the bumper may look okay, there are the structures mentioned above that deform to absorb impacts, and these must be replaced to provide adaquate protection in the future.