Landlord not returning deposit

Hello, I took a flat with two other guys on rent in July 2015. I paid the deposit of 40,000 to the owner. The 11 month rent agreement mentioned that I will have to give 45 days notice period before leaving. While signing the document , I didn't see that the date on agreement was of "2014". The agreement has name of only one flatmate but signature of everyone including owner. I informed the owner on 19th June via whatsapp that I will vacate the house by 15th July. I still have the whatsapp conversation. I vacated the house on 4th July. Still I paid the rent for June and July . So my 45 days notice period is also completed. Now the owner is refusing to return my deposit until a new tenant comes.The other two guys are still staying there. Whenever a prospective tenant came, the owner asks the deposit directly instead of telling him to transfer the deposit to me. So the tenant didn't join as he came to know that the owner has paid the deposit back to me. Please help.