Here is the issue. Is the lease a separate agreement from the guarantor application and if so, then you need to see if they are incorporated by reference on the other such that one is not effective without the other. If it is not obvious or blatant and no such specific provision exists in either contract to make them only effective upon the execution of both, then the likelihood is you still are liable under the lease until they mitigate their damages by finding another tenant. I am unsure if the eviction was the proper method here. It seems a bit hasty. Consider reviewing it with your school counselors and see if they can help mediate this matter. If not, talk to your state attorney general if it has responsibility over landlord tenant issues.