This person who was fired for refusing to sign the paper will probably qualify for unemployment benefits, as I doubt if this is going to rise to the level of major misconduct. Hope she didn't have a history of warnings for insubordination or failure to follow instructions.
In the case of an unemployment hearing, whether or not the employee had signed a part or all of the handbook might be considered, regarding whether they KNEW they could be fired for doing or not doing a certain thing. ("Did you know it was against the rules?" ) An employee's signature on the manual or policy statement is going to be fairly conclusive.
However, if you told the hearing officer that the employer passed around a blank sheet of paper and instructed all the employees to sign it, without going over the policy or telling you why you were signing the paper, then it would not be valid as a statement that you had read and understood the new or existing policy. So it would not accomplish anything anyway. It really wasn't worth losing a job over, but I do agree with the employee who was terminated. In this situation, it was a bad idea and a bad practice on the part of the employer.