My father gave a blank cheque and an unsigned promissory note to someone without a date. He passed away on 15th July 2015. We closed his bank account, stopping all existing cheques. He only owned a Nano car, financed through Tata Motors on 17th November 2012 for 5 years. What happens if this person tries to deposit the cheque and sue us, even though the account is closed and my father has been gone for six months?