This is another example of an OP deleting a question after receiving an answer.
This has been discussed before: Why do some users delete their questions after receiving an answer?.
However, I wonder if there is a way to add a feature to gray out the question and then allow users to flag it for a Moderator after the question is deleted because this is unfair to the person that posted an answer. Currently, all a user sees is Page Not Found and that makes it very difficult to take any action.
Lastly, should this question and answer be resurrected because of the unfairness?
I see another (the same) question was just asked again: Find a jordan basis for the given T linear operator, as opposed to asking for clarification in the originally answered question.