I wanted to post here rather than the dead-to-the-world A/V forum. It's also more "electrical" in nature than A/V

Anyhow, to make a long story short -- The ground wire to my amp (which pushes my 10" sub) fell out the other day. I didn't have the time to put it back in. So I just left it as is. As I was driving down the road, I noticed that my sub would sometimes hit and sometimes not. WTF? It shouldn't be on at all without a ground wire in. Pop the trunk and find that top of the amp is grounded by the top metal "ceiling" of the trunk and also by the NAV DVD player cage. Obviously, I have now moved the it away from the NAV DVD cage. (pictured below)

Questions:
1) Can something bad electrically happen? I do have the proper fuses in the proper places, but I noticed that it sparked every now and then if you moved it around.

2) Once I reinstall a legitimate ground wire, is it ok if it still touches the metal up above?