Most bizarre body damage

[fierro]

Hi folks,

Just got my 09 Z a couple weeks ago (w/ amuse body kit). I took it into the the Mossy Nissan Oceanside dealership to get some electrical work done, and I think they caused this damage. I didn't notice it until 24 hours later but I've called them and am in the painful process of trying to get them to admit that they caused this, since there's no other way it could have happened.

370Z Hatch damage - Album on Imgur

What you see here are significant cracks in the body of the hatch around the spot where the spoiler is bolted on. The metal is completely torn. It seems like a lot of force would be necessary to break metal like this. Its torn on both sides where the spoiler connects.

It's already rained once, and water has gotten in the hatch door (and slowly leaked into the trunk), and I can already see a little rust. You can see some rust in the second and third pictures.

Anyways, I'm posting this to see if anyone has ever had a problem like this, and what the best course of action is. I'd hate to have to replace the whole hatch over this. Could I weld that area shut? Would that look awful? Hopefully the dealership will own up to this, but in the likely case they don't I need a contingency plan.

Thanks for looking.