What are the circumstances

[Alexey86]

I think most people reading this sentence would be thinking that the detective has been looking for somebody, that person being Mr Johnson, who just happens to live on the second floor.

That's exactly what I meant by "living on the second floor." It's just additional information about Mr. Johnson in the form of a participle phrase. The destination is still the person, Mr. Johnson. Compare it to this: "I looked out of the window and noticed the man(,) living on the second floor (= my neighbor who lives on the second floor)." Do I need to put a comma here?

Do you know a game called "Hot and cold" where you have to find a hidden object based on verbal clues? Suppose I found the thing under a teddy bear that is lying on a sofa. Can I say, "The clues led me to a teddy bear(,) lying on a sofa"?