First off, I suggest that you edit your last post & remove the traders name from the "quote" title.
This isn't a BTR and, by naming him here, you're essentially "calling him out."
(Even though I doubt this was your intent)
It'll look better on YOU in the long run, if you do. It's better to allow your trade partner to remain anonymous while inquiring about advice on dealing them and, should they desire, let them name themselves openly. That way, you will not be accused of fingerpointing and laying blame (as a BTR) without posting the required proof.
At this point, I won't say that he's lying about the Money Order.
That would be unfair to him.
You need to require him to prove it, though. If he does not, then it's the same as if he didn't pay you, as he made no assurances that the money would get to you (no D.C., signature, etc). It is his responsibility to ensure that YOU (and nobody else) receive payment for the goods.
As for him stating that he replied... either you're lying or he is.
I have MY suspicions which it is, but I won't say which it is publicly, as I'm trying to remain impartial in my advice.
If he did send you PM's, have him forward them to you... He can go to his "Outbox" or "Sentbox" (depending on whether or not they were read) and copy & paste everything (the "address lines", as well as the message text) and put it all into a new PM.
Linrandir can, then, check that against the system to see if he really did send them and whether or not they ever made it to you.
While I doubt it would happen, I guess there's always the possibility that a BTown hiccup caused those PM's not to arrive to you... numerous times.
If he claims that he no longer has those PM's, most of us will presume that he is lying about the PM's and, by default, presume the same for everything else he says.
I would even mention this thread to him -and include a link- in the PM you send him.
Eric
Oh... and presuming he's telling the truth about the M.O. being cashed, HE has to be the one to go to the police, issuing bank, P.O., etc.