No, unfortunately there is nothing you can do. Severance is not required by law--it is up to the free choice of the employer--so they can set rules on it, such as who is eligible for it or not. They can also freely decide who is going to be laid off or retained, and and if an employer whom the employer wanted to retained leaves work, they can consider that he or she resigned. In short, this is all your employer's choice, not yours, and if you don't qualify for severance under the rules they put in place, you won't get severance.