Inside has developed from being a preposition simply meaning withing a building, to meaning just about anywhere in the world. It is an incredibly unhelpful way to assist anyone who is in genuine need of assistance in locating something. It can also be a reference to someone's testes.
Tesch: "Have you guys seen my pregnancy test?"
Shoey: "Yeah, it's inside."
D-Ran: "Inside, Brutha."
Tomoi: "Inside THESE GUYS." (Points to testes)