unsolved mysteries that happened to you irl?

my family owned a restaurant and basically this one lady worked with and one day she randomly doesn't come
she's worked with us for TWENTY years and she never did something like this
but anyway we soon found she worked at a different restaurant and my parents respected her choice if she wanted it
six months later we find out that shes dead from an overdose.
she never took drugs but her toxic boyfriend did and she was found dead at his house
we never knew the reason to any of this

any unsolved mysteries any of you have?