If you don't claim your stuff, people should be able to take the stuff. You are able to claim your stuff because you get a golden shovel and a bit of claim blocks at the start of the game. If you don't have enough claim blocks to build a house, don't build one. Just store some stuff or go with a friend and find a place to claim with them. It's not that hard. Staff also shouldn't ban people for stealing from claims that aren't claimed, it is the person who didn't claim fault.