The soup stone is missing. My grandpa was from Vilnius which was part of Poland when he left. They always had soup on the stove every day all day and one of the things in it was always a stone to hold something (herbs?) at the bottom. It was such a part of the family that they weren't sure who was going to inherit the stone - it went to the oldest son.

Maybe it was actually one of these? https://en.wikipedia.org/wiki/Stone_Soup