The same standards do apply for ex parte matters.
I would contact the court clerk, point out the error, and see if they will issue a new date. Alternatively, see if the tenant will stipulate to a new date. If not, you will need to make a motion (ex parte or otherwise) to move the date.
UD trials have a priority in setting. Also, most courts have certain days they hear certain types of cases. It may be that your unavailability was the day they hear these trials, and the only day w/in the precribed period for UD trials. You may want to consult with a local UD lawyer. Im moving this question so you might get a better answer.