I think you talking about geocaching ;)
I think it has something to do with the gravity of the two objects.
Slave catchers
Something called echo-location
Those objects are called reflectors. They bounce light rays back in the direction from which they came.
It is called a symbol. Symbols represent ideas, concepts, or objects that hold deeper meaning for individuals or within a specific culture.
Cootie Catchers
There is something called "air resistance" or "friction".
Chasing zoey
They are called dog catchers, dog hunters, or dog nappers. =)
The simple answer for this question would be Slave hunters or Slave catchers..
Some catchers are allowed more leeway to call pitches by their managers than others. But usually pitches are called by the manager or pitching coach and relayed to the pitcher by the catcher.
I've heard we are called kittens :)