Well, it is possible that your kid didn’t hear the other kid good or your kid hasn’t tell you the sentence as it was said because staph infection is highly contagious!
How long this condition is contagious depends on various factors such as when it was diagnosed and when the treatment started etc. But the only person who can confirm that child or adult isn’t contagious anymore is the doctor. He must be sure that the bacterium isn’t present in the body anymore. So maybe the kid was sick and had some skin condition but he is getting better and the doctor confirmed that he is no longer contagious so your child has told you that information. But if you want to be sure that your child didn’t get infected with the Staph you should call parents of the infected kid and get confirmed information.