Saturn using a hack client??

Hello there!
I have noticed that my NCP Kept telling me that saturn is trying to do something he/she is not supposed to do on the server. i have decided to Post this to make sure if he/she really has a hack client!
Note: When I asked her/him to turn the hack client off he/she left the game without answering back, so that kind of made him/her suspicious.

When that shows up, typically its someone placing a sign at spawn and it instantly despawns. Also this notification shows up when people place a billboard.