Using a blessed stetoscope on a 'detected' trapped door says there is nothing to check.
If you use the Detect traps skill and discover a trap on a door and then try to use a stetoscope on said door, the game respond by stating: There is nothing to check.
How to reproduce: Find a trapped door with the 'Detect Traps' skill. Use a blessed stethoscope on trapped door.
If you would use a blessed stethoscope on the door prior to detecting the trap, you would get some information about how many creatures are in the room behind the door.
The PC in the savegame is standing next to a trapped door.