ni act 138 notice from a ex employee ,cheque stolen

Dear Sirs, I am from a pvt ltd company, in the year 2103, first month of the year ,my accountant told me certain blank cheuqes are missing ,we stopped them immediately in the month of January 2013. in the month of July 2014 ,we got to know from my bank statement that one of cheque from same lot has been presented in bank by by one ex employee in a heave amount written on it, who has been fired last year(2013). So Respected experts kindly help me find out the solution of this !-the employee has put heavy amount even after one and half year of stopped cheque. 2-now he has sent some legal notice under section 138. 3-we never gave/issued any cheque to him, it means he has stolen the cheques. 4-yes he has some disputes with HR because he was not regular during his tenuare in office. Sirs my question is if there is any provision in ni act , because forensic examination of cheque can easily proof that signed time ,stop date timing are same in January 2013 and amount written time have huge gap.( approx 2014 may),and signed by me and amount and date has not been written by me .. second thing he is calming that we have given him cheque in 2014 (false date was in june2014) for the liability for 2013 august . But the truth is that one cheque has been missed and stopped in januaray 2013,how can we give him a cheque to him in January 2013 for uncertain employment labiality of august ( 2013).he was with company in January ,there was no surety/intimation about his tenure at that time. Means forensic expert can easily proof that the at the time of stop payment cheque was blank and gap between signed time and date and amount timing was approx 18 months. He look some blank cheques in 2013 now misusing that, I have all the proofs ,entire staffs ( ex and present ),they are the witness and are ready for give the truth to the court. Kindly advice, I need a help from expert