I think Weltall was quite clear, Everaj.
The system message has a limited range around the player who picks up something, just like most other actions. The range for getting the message is the same as the maximal distance from which you can grab items, 5m. This means that if you want to be sure to get a message when somebody takes what you have dropped, you must sit exactly on top of your item. That is what I mean with "a bit short". Twice the range for perception would make sense, or maybe the sum of distances for guarding and picking up things.