zero sperm count

my partners results came back yesterday with zero sperm count. They said they will do another sample but if it comes up the same he will be referred to a fertility clinic. he had testicular cancer a few years ago but didn't have to have any chemo or anything they just took one testicle off with surgery and he has been clear since. he had 3 children previous to this but this would be our first child together. he has sperm frozen from before his operation but I am so scared it won't happen for us. has anyone had a similar story??