Cheque bounce case. Please help.

Sir, This is a 15 year old case. We were not aware of the case as we had not received any notice earlier. Few days back received notice for cheque bounce of 50 thousand. 15 years back when the cheque had bounced we had send our staff to mill for giving payment. Our staff gave payment to the staff that used to collect payment for the firm. We had not received return cheque but we received rubber stamp and signatured document from the staff saying that when we get cheque from bank we will send it to you. 15 years back it took 2-3 days to receive cheque from bank. As we had Rubber stamp document from Staff we didn't care for cheque. It is now that we know that there is case against the return cheque from the owner of the firm. We had asked him to call the staff but he says that staff has expired. Also he is not bringing his cash book to proof that cash was not given to him during that month. How can we win the case on the basis of Rubber Stamp document by his staff. Is rubber stamp as proof is invalid. The firm owner have not presented any document such as cash book to proof that he has not received cash from us. He says that document has been drained in floods. We is not willing to accept that we have paid him through his payment collection staff and the staff has also expired. How can we convince court to give judgement in our favour. Kindly help