This question already has an answer here:
The OP, in his infinite wisdom, edited out the duplicate link!
And then someone flagged it for moderator attention, and a moderator rolled it back and locked it with a warning to the OP. This is the way in which such things are handled...
Why is this allowed?
This should be prevented, or the duplicate question link should be present in the close reason.
Now if any future users (who are not used to the Stack Exchange) come, they will see that the question is closed due to it being a duplicate but they will not know what the duplicate link is.
I propose that we put a non-editable header at the top of duplicate questions that the OP cannot remove, unless the question is reopened.