First, did you mean, “Do you not know…”? “You not know” sounds more like a statement than a question. Are you telling me that I don’t know or asking me?
Second, I am fully vaccinated, and I still avoid being in crowds and still wear a mask. So, I absolutely do not think that being vaccinated makes you invincible. However, in this case, had they been vaccinated, then they may not have had it, and they would not have been tested anyway if they had been vaccinated.