There are many occasions where I have used sneak to steal items when there are NPC's around. Even when successful, the NPC always seems to know that a theft has taken place and a further check is required. I can understand this where the object being stolen is in plain sight, but it also occurs when stealing from conatiners and/or bodies. How does the NPC know that gold has been taken from a dead body or that an item has been taken from a closed container?

Thois action implies that NPC's are checking every container and body as the move around.

Having succesfully hidden and take an item why is a further check necessary?