The Kind Hearted IRS

I posted a while back about our IRS problem. The IRS said we filed late. We didn't.
Every two weeks last summer we got pushy letters (one to each of us) threatening to attach property if we didn't pay the 10% penalty. I wrote and called them several times. Finally a sympathetic ear said he would check the little box that we would agree to pay and that would stop the letters. I responded that we were not agreeing to pay because we filed on time, and asked him to check our past history. He checked and said we have never filed late but his record only went back a decade. When we arrived home I went searching for my mailing receipt for the 09 tax returns. The Post Office receipt includes zip codes for where the mailings went. I mailed the IRS a copy and drew arrows to each zip code with explanations of what they were for, and highlighted the mailing date. Then for six weeks I heard nothing. Finally a "Dear Taxpayer" letter arrived saying they were removing the Failure to File Penalty, and to expect an adjustment letter in approximately three weeks. (I'm cynical. I wonder what they mean by "adjustment?") I'm glad I asked for a receipt. Without that we would be assumed guilty and have no way to prove otherwise.