This Seeking Tech guide will show you how to unlock the A Thief Heeds No Warning trophy. This will pop when you “destroy 4 signs in A Stealthy Approach.”
Use the following video as a reference along with the text:
You will find the first sign at the start of the Stealthy Approach level.
The next two is located at the gate shown in the cut scene.
The fourth one is located to the right of the same gate. You can also break the sign next to the ladder to unlock this trophy.