Duendes (like gnomes) are part of a lot of latin american folktales but also from all around the world. They are mischievious and hide your stuff usually to play pranks on you, sometime they get attached to a home and make people's life miserable with their jokes if they don't like the new tennants. One common thing among the Duende stories I've heard is their pointy hat and prankster nature.
I've heard from them from people from Central America, Spain, US, and Philippines.
There's some ways to get rid of them, my grandma says you have to speak rudely to them, and they will give your stuff back. Some people say you can leave sweet stuff for them at night, like condensed milk, and they will eat it and be happy with you.