CPS Security — nsf check

On August 22, 2019 I received a letter from you stating that my company had a returned check from Winn Dixie-Bi-Lo. When I researched the check the bank had no record of the check being returned and did not have any record of it period. There would usually be a NSF sent along with a fee but there was no record at my bank at all of this check.
I searched my records and the check is missing from my register so in an effort to try and figure out if the check was stolen or what happened I could not find the check. I called your office on four occasions, the first two people I spoke with agreed to send the check copy but never did.
I got a second letter today dated September 11, 2019 and spoke to two different people whom were both very rude and told me that they would not send a copy of it and the next step would be small claims court. Both gentlemen that I spoke to today told me that no one stole a check out of my register and I would be in small claims court and were both very rude.
I don't have an issue paying the check I only want a copy of it. I do not understand their rudness. Would you please have some one send me a copy of the check with the signature so I can do more research.