I know there's an actual word for this. I used to know the word, but I've lost it.
The word describes a category of methods that someone uses to detect if someone has been in a room, or opened a door, or drawer, or folder, etc...
Examples: 1) Putting a strip of paper in a door jam, so it falls if someone opens the door. 2) Putting powder on the floor that will be removed or scattered. 3) Putting a ball behind a door in a specific location, so if the door is opened, it can't be placed back where it was with certainty. 4) Putting tape across a drawer that will be broken if the drawer is opened.
I imagine this word would be associated with forensic science, security, or criminal / legal work.