Unexlpained broken window

I went to storage yesterday to get some things out of the 5er, and this is what I found. The manager said they have never had any problems, and reviewed the camera footage for the last 2 weeks when I dropped it off. There is no one in the spot behind me, so the camera showed the rear of the 5er good, but nothing was found on video.

I called Cedar Creek to order a window, but they will only sell to a dealer. My dealer said the window would be $240 plus a few hours labor to replace.
I'm still wondering how the window was broken, maybe someone turning around with a ladder rack, a bird, or something thrown at it.