A scuba course is performance based.
Weight belts do fall off.
If you were unable to replace your weight belt, then you have not completed the requirements and can't be certified. But you should have just had to practice and show proficiency at replacing a weight belt, not take another course. If you feel that it was a truly unprofessional experience, be sure to notify the certifying organization, they have quality assurance on training matters and can follow up on this for you. A scuba course is performance based. Weight belts do fall off.