It is possible to come back, depending on how you communicate. Because the general place can't be formally employed without training, it also needs whether you are qualified for this job. Another possibility is that he is particularly short of people and it is not easy to do it. Why did you give him a health certificate in advance? This has nothing to do with your going to KFC in the future. But pay attention next time, you can show him a health certificate, but you don't have to. You can also give one.