Not a complicated issue at all - I bought Bitcoins through him eight years ago, when he closed Tradehill he offered to look after them for a fee - when I tried to get them back he simply failed to respond.
The mistake you made! Why would you want him to look after your bitcoins? Did he promise you a return or some profit?
I have tried every way I can think of to get in touch - he must know that I am trying to contact him and he knows why, just easier to not get in touch and keep hold of my bitcoins.
Since you will be traveling to the US, you can easily find his information once you hit the cybercrime officials. Someone has already mentioned all the information you need but not sure if that would be relevant now.
Put simply the man is a thief - seems that he is setting up others (I note the Bahamas business does not deal with US residents).
This isn't a business, right? The deal was more like a personal trade between you two.