Scammers will talk the player into dropping an item, because he/she can pick it up again before it appears to other players. Before the player takes it, they will expel the player from their house, and will take the item once it appears to them.
This is often common with Drop parties. Some players will talk a dropper into having the drop party in their house. When the dropper drops things, the owner will expel everyone and collect the items.
This is why you should never drop anything you are willing to lose inside another player's house.
Suggested action: Report the player for item scamming (rule 2).