You may want to have the Postmaster in his town look into this. As much as the postal system is a bloated bureaucratic nightmare, they really don't like people committing fraud in their name. If the post office says they delivered it and he says he never got it, they are going to be none too pleased with him.
Now the other thing is that when I used to go to court on eviction proceedings, the courts would always consider the USPS as a reliable delivery device. In other words, if you have proof that you mailed it, that is good enough for the courts to rule that the person received it. It's a strange thing with the signature idea too though. In our proceedings - not that they are the same as yours - sending something certified mail or signature required was problematic. The courts have ruled that a person can actually say that he wasn't the one who signed for it. In other cases, the person has been able to say he didn't receive it in a timely manner because he refused to sign for it (not related to your case it would seem). Seems stupid but..... Long and short - your proof that you mailed it should be sufficient.
I would suggest you try to get the post office (both your local and his), the local police, AND the local Sherriff on it. One of them is likely to at minimum give the guy just enough encouragement to clear this thing up. Send them copies of your evidence and let them do a little knock and talk with the guy. My guess is this isn't the first time he's pulled some kind of BS and the cops might even know who he is already.
Good luck.
