Explain how a trait might seem to "disappear" for a generation, and then "reappear" in the following generation

It could possibly be like manners. Manners faded away in our generation but since seeing that it is really bugging a lot of us that there are no longer no kind people we might teach our kids manners and how to be kind. The manners might come back as we see that most of our fellow classmates or workers don't have any manners.

The trait is likely recessive and will reappear in the next generation when paired with another like rcessive trait.