Did the sale site list the terms and conditions of the sale? If a time was stipulated for receipt of funds and or FFL then you may be out of luck to that end. Having said that I would think that you are due your $400 to be returned.
I think you will find that the BATFE does not deal with this type of thing. They only license dealers. They do not deal with failure to provide services/goods. The State Attorney General is one avenue to address this. Having said that I think you will find limited assistance forthcoming from the AG. They will file a case and they will contact the smith but for a single case of $400 I do not think they will act. I know, I went through an ordeal over $4000.
Send the guy a certified letter outlining what happened and state that you want your money returned by a given date since he failed to deliver the goods you purchased
