Yeah when my wife called to say we lost 2 fish I thought the tank was crashing or something. I have seen the goby thats paired with my pistol shrimp chase the diamond around when he gets to close to his territory. That may have been it but there are so many rocks and caves to go in I thought it was a bit weird that he would go strait up and out if he was being harassed.
Here is a pic of the other goby (you can see a bit of the pistol shrimp on the left)
I would love to get another diamond goby cause they are neat to watch and do a great job on the sandbed. But I'm not to sure if I can.