Disclosure: I am not an attorney. This is purely my opinion.
If the lease was never signed and there is no other written agreement that is signed at least by you, it would appear that the landlord does not have the right to keep your deposit. Of course actually getting the landlord to refund it may not be so easy. A small claims court action may be necessary to achieve the result you want.
Bernard Gibbons, Realtor, e-PRO Certified Internet Specialist
J. Rockcliff Realtors, 15 Railroad Avenue, Danville, CA 94526
Phone (925) 997-1585