I came across this thread on hacker news:
"This question has been asked before and already has an answer." This is the single MOST ANNOYING thing about stack exchange. WHERE was this question asked before? How about a link to the original question? Hello?
This user appears to have missed the 'This question already has an answer here' box, and is annoyed that they can't find the question this one is being marked a duplicate of. There are other responses in that thread with others making the same point. It looks like this is a surprisingly common thing.
Looking at the question the thread is about, the long post does mean that by the time you see the reason, the link is long gone.
To avoid this misunderstanding, it might be worth making the 'has been asked before' part of the close reason a link to either the box above or directly to the question, to avoid this confusion.