lol... I was kind of thinking something rattling in the trunk too.
When did you get the noise? Only on throttle application? You wouldn't think it would just go away like that.
You really should be able to see any cracks if you crawl under your car with a light and look at the subframe mounts.
Did the mechanic look at the subframe area? It would be pretty easy to see the damage if it was there.
