Today I ran into this question which has an upvoted answer and judging from the comment by the asker, it helped them and answered the question. Unfortunately the answer wasn't accepted and the user has left the site.
In my opinion it would be good it the answer could still be accepted such that the question is marked as such - there's an good answer to the question.
What do you think about this? Is there a policy in place to deal with this and would there even be a way for a moderator to manually accept the answer for the user who has left the site?
Edit. The same problem arises with this question.