If the suppressor is legally the transferee's why does a 4473 need to be filled out? The OP's buddy (from hereon referred to as OPB) does not own the suppressor.
What's actually irrelevant is all of this back-and-forth banter because whether we agree or not doesn't change OPB never seeing his money or suppressor. I'm not at all referring to the criminal aspect to all this, just talking about what Aaron's main man can expect. If the dealer isn't intimidated by certified letters from attorneys there isn't shit anyone can do without spending many thousands of dollars on an attorney, piercing the corporate veil, and going after personal assets. Period.
If the company went out of business without proof of gross (or even ordinary) negligence, then the veil stays and he can pound sand like everyone else the LLC owed money to.
Good reading here from someone in a similar situation that consulted an attorney:
And because the transfer doesn't legally happen and can be voided by either party up until the 4473 is signed and transfer made - it matters not whether the ATF put a stamp on a piece of paper.
It's an open and shut case.
http://thefiringline.com/forums/show....php?p=5574457