Unpaid Rent?

[GrantWriter]

I moved into my current rent stabilied appartment two years ago. I had heard stories about the owner harrassing tenants, but other than a lag in repairs. I had no problems.
Our rent due notice is put under our does and reflects the prior months postings. My records show all payments prompt.
My wife passed away, in my apartment suddenly last month. Ive ben a mess but went back to work quikly and the routine helped.
This months bill showed I owed this months rent plus a balance of one month behind. On examining the statement I noticed the Dec. rent(which did go out late was not posted). I faxed a copy of the MO( I do not use checks). The next day I called and he stated it was realy the Oct 03 rent which was never received. I could not find that stub( chao after my wife's passing). I checked the bills, which i did have. All showed
a posted rent payment and no balace due. It even listed the receipt date and the MO number.
In todyays mail, I received a copy of the bill for this month with the entry for Oct deleted.
While I still have the old bills with the posted payment, he indicates that his records show no depost of my check?? This makes no sense. He received it but lost it? If he lost it, Im not responsible, right? Also is the monthly billing statement that I have enought proof that the rent was paid.

I honestly dont feel like fighting right now, but I am going to his office to deal face to face.
Any fedback is appreciated.
S.T.