If a normal player (someone without op rights) types in the chat for example this command
"/tell @e[type=Player,name=!'your_nickname_here',x=0,z=0,y=64,r=1000]" without a message (so the error message will show)
than can he detect other players (shown on the numbers of the error messages) in this area, without they know about it.
As far as I know there is also no entry in the Serverlog, so the Serveradmin don't know someone use this 'glitch'.