There are a few ways actually to prevent yourself from being scammed this way. The way I showed people only works with decreasing the x or y variables, which for x would be going left and for y going up, so if you are in your own house and are going to trade, do not let the person you are trading with be below where the item(s) are or to the right, making it to where they can not walk through anything that blocks them thats are below them or to the right of them.