Correct there are no squatters rules. they were wrong in calling you a squatter. If anything you are a trespasser, though an unwitting one. And there are trespassing laws.
Have you tried seeing if the owners are willing to rent to you and negotiate a lease with them?
Next time, check the leasing agents credentials and make sure they are authorized to rent the property. Unfortunately they are a lot of scammers out there. While you were victimized here, so were the owners.