Service BOND amount paid vide DD but Employer claims non receipt

Dear Sir/Madam, I had signed a BOND of Rs 1 lakh (for serving the Company for 5 years) at the time of joining the employment. While leaving the employment after 2 years service, I had paid back the amount of Rs 1 Lakh to the Employer by DD (of Rs 45,000) & a Bankers Cheque (of Rs 55,000). Employer has given me the receipt for the same. Employer has also provided me with resignation acceptance letter, release letter, Experience certificate. Now, after a gap of 5 years - I had received a notice from Employer. Notice states that Employer A/C is not credited with the BOND amount ( Rs 1 lakh) and hence, I shall pay the due amount immediately. Please advise what shall I do now : (1) Is it sufficient to have the "Receipt from Employer stating receipt of Rs 1 Lakh" ? (2) Do I need to approach Banks to verify whether those DD/Banker Cheque were en-cashed or not ? ( I may not get any success here as the data belongs to 5 yr earlier period) (3) DO I need to approach Police / Courts etc ? (4) Incase, Employer persit with demand to make payments - then what are my options ? Please advise.