This is one of the most painful experiences for a child, and unfortunately, it does happen. When a child is not believed, they often internalize the idea that they misunderstood or that their feelings do not matter. That can silence them for years.
If this happens, your response is incredibly important. You can say, “I’m really sorry that adult didn’t listen the way they should have. That doesn’t mean you were wrong. I believe you, and I’m really glad you told me.” Then help your child identify another safe person to talk to. The message they need to hear is that one adult’s reaction does not determine the truth or the importance of their experience.