Hi Rockit!! Welcome to our little world!
Does the noise go away if you let the bike cool off? In the past there have been posts on different things like the heat shields around the radiator rattling when they get hot. Just the other day I had the shift linkage come loose and that rattled (that's how I found it).
You might try getting the bike hot and blip the throttle (in neutral) while a buddy crawls around and tries to locate the noise, assuming you can duplicate the noise that way.
Since you just bought it the easy way would be to have the dealer find the noise... even if he can't at least you have a complaint on file and if it turns out to be something serious later you should have some recourse. If the bike was sold to you off of MSO it is treated as a new unit and you should have the full factory warranty. MSO is "Manufacture's Statement of Origin", kind of a birth certificate from Triumph. The state then issues you a title. The dealer probably used this bike for a demo and maybe some personal use but I doubt he took it off of MSO, as a dealer he doesn't have to. If it had a title when you bought it... it was a trade in... someone else previously owned it, but you would still have the remainder of the warranty. Some 2005's were sold in the summer of 2004 so time would be quickly running out on them...
I hope this helps..
Tomo