What real cases have you encountered that have not been solved so far?

When I was a child, several uncles came to mine and lived in our village. I always ask them some questions out of curiosity, so I know them better. One day, one of the workers suddenly couldn't find it, so he said he went out to look for it, but he still couldn't find it. A man disappeared for no reason. Then the police came and the case didn't progress. In the end, it went away. I was very scared, so I was very impressed. One day, I suddenly asked about it. The old man said that someone in the village had ulterior motives, killed the worker, robbed him of his money and threw him into the hole. Nobody said anything specifically.