Need for legal guidance rental contract

[Fakhir Butt]

Hi,

   My lease expired in October 2014, I didn't receive any renewal notice. So in November I requested a renewal with a 60 day rider clause (letter). Days later I received a call saying that the rider is approved, and in order to make the amendment I need to sign the lease and send a $500 check. Which I promptly furnished (signed lease for a year and sent $500 check) I also wrote a letter stating "I am signing the lease per there approval of Rider."  Couple days later I received a call that landlord denied the rider, for that my response over the phone was "I am not sure if I want to renew the lease or not." Since then no further communication. 

In march I bought a home and moved in May after 60 day notice. Now the landlord is making me responsible for the remainder of the rent until October 2015. 

What is my recourse in this situation?

Couple of things.

-  The employee I was dealing with is no longer with the company

-   I did not send my reply letter via certified mail

-  I have the phone records and the envelope the check was returned in. 

To me our agreement was based on approval of rider since it was denied then the contract is null and void too, and I was living on month to month basis.  

Please advise, thanks!