What happens if my previous boss no-showed at my unemployment appeal?

You are umed innocent until proven guilty. With that principle in mind, you're statements are presumed to be true unless a witness, such as your boss, contests your statements, which in turn proves your statements to be false. If the common wealth cares enough, they may get the judge to issue a subpoena which forces a witness to come to court to testify, or they will be charged with "holding the court in contempt".