Yes, note that just like the novel it is based on this movie doesn’t club you over the head when it explains things. You have to really watch for it, and sometimes it doesn’t explicitly explain them at all, and you have to draw your own conclusions.
So the guy who hires Carson Wells and works in the big office building, you probably remember that later in the movie Chigurh arrives at the office and kills him.
While never explicitly stated, it is presumed this is also the man who hired Chigurh in the first place to recover the money. After shooting his employer, Chigurh speaks with the accountant who was in the office with him, and says, “he gave the Mexicans a receiver.” The accountant explains that he felt that having more people looking for the money would increase the likelihood of it being recovered. Chirgurh says that is foolish and you should instead carefully select the right tool for the job. So from that discussion, we know that the Mexicans were given a transponder.
Interestingly, Chigurh also knows that this guy hired Carson Wells to kill him, but he seems less concerned about that–to Chigurh the fact that his employer had someone else doing the job he was tasked with was in and of itself a grave and lethal offense. Hiring Carson probably didn’t make him happy either, but just giving the Mexicans the receiver was enough to seal his fate as far as Chigurh was concerned.
The man in the office by the way appears to be some type of “facilitator.” He’s not the money side of the drug deal himself, because in an earlier scene he mentions that the Mexicans are pissed because they are out their drugs, and “our clients” or something are pissed to be out their money. So whatever it was he did he wasn’t making drug deals himself but facilitating them in some way and obviously he had responsibility for fixing things when they went South.
I won’t openly spoil the book where it isn’t shown explicitly in the film, but:
In the movie, we never find out precisely what happens to the valise full of cash. The presumption is that Chigurh ends up with it, although if you look carefully at the opened air vent in the motel room where Llewellyn is killed the duct is far too small to hold the valise so however he ends up with it he probably didn’t retrieve it from there but perhaps another hiding place in the room. Anyway, we never do know for sure what happens to the money. In the novel it is explicitly said Chigurh ends up with the money, and he returns it to a third party–presumably the money side of the deal, Chigurh does not keep it for himself.