Although I don't know Canadian law, normally in a civil suit, a plaintiff should satisfy the burden of proof by establishing the injury, causation between the injury and the defendant's wrongdoing, and the damages. In your case, if he did not record the previous condition of the property, how can he prove the damage-the reduced value due to the subtenant's misconduct. Additionally the landlord lost in the deposit return case. He will look bad in this case because it seems that he intend to retaliate you. Therefore, if he did sue, it would be his words against your words. I think you will be fine.