The box of almost identical keys

An original narrative about an invented caretaker's task.

The key I wanted should have carried a green thread. Every key in the box carried a green thread. I lifted one bunch, then another, making a noise that brought the caretaker to the doorway.

He did not touch the keys. He asked me which door I was trying to open. I described it: narrow, grey, beside the stairs. He asked what was behind it. Only then did I mention the room where the cleaning machine was kept.

“The machine-room key,” he said, and pointed to a tag I had turned away from myself while examining the threads.

The small label had been there throughout the search. I had been looking for a colour instead of reading the name. As I closed the box, the other green threads settled into a tangle that seemed much less mysterious than it had a minute earlier.

How does the writer make the narrator's search seem briefly confusing and then simple?