Answer: report this situation directly to ARRT.
Explanation:
According to the situation described in question, if an employee finds that radiographer's ARRT certification has got officially cancelled and inspite of that supervisor is ready to hire him due to staff shortage then , the matter should be reported to ARRT(American Registry of Radiologic Technologists) department.
American Registry of Radiologic Technologists(ARRT) department handles the certification provided by them in areas of radiotherapy, imaging etc.They will take the necessary lawful action against the radiographer for not having proper license and certification to join a job.