I agree with your statement daycaremum that it would not have even been a question for me about telling the parents too, but I definitely wouldn't have done it in a way to embarrass the child. It sounds to me that the child really wants to please his parents but had a little accident, no big deal. If he gets a punishment at home for his accidents maybe that's the parents way of trying to help him train, I don't know. Only the OP and the parents can discuss this together.