If you don't show up and the case is ready to go, you will be found in default and will lose automatically. While you may be able to get the judgment set aside after the fact based on the error, (1) that's not actually given--the court may feel you had an obligation to bring the fault to the court's attention; and (2) even if you can do this, it's always more difficult to correct matters after the fact; and furthermore (3) you'll just end up having to make a different court date. Since this won't let you off the hook forever, you're best off contacting the court and clearing up the error up front, so you can deal with this once and then move on.