I answered a question, and the asker deleted it after I answered it. A solution would be to make the asker lose reputation if he deletes a question with at least 1 answer. By the way, I think he deleted the question because it had -2 votes.
An OP can only delete a question if it hasn't got any upvoted answer on it, or more than one answer. Unfortunately your answer had not yet received upvotes.
I don't think penalizing question askers for deleting a bad question is a very good idea either though. When they ask a bad question, then delete it they are helping keeping the site clean. If question deletion would cost reputation we'd have to clean up many more crappy questions.
That said, we don't want to encourage such behaviour too much. Note that if such a question asker keeps deleting downvoted questions he or she will be blocked automatically from asking any more questions.
In your case the question was probably not that good (score -2) and the poster regreted posting it. It is just fair that he/she can delete it.
For the cases mentioned above there is a delete protection already in place.