This sort of relates to this question on the meta but is a different case at the same time.
The question 'in question' is this one, where a user posted a link to another question that solved the users question. I don't know if everyone just didn't notice it or not but would be nice to know what I can do to help out.
Do we flag, vote down, ask the user to post that as an answer (I doubt), or what?
Ideally, you'll do one of two things:
Close the question as a duplicate (if it actually matches the previous question pretty closely). If it's not a duplicate, but an answer to the other question merely happens to contain within it the seeds of a solution to the new one, then instead...
...Post an answer that helps relate the information provided in response to the earlier question to the specifics of the new question.
Note that #2 goes for just about any question where an answer can be found in the comments: don't wait for the original author to do it - if he wanted to leave an answer, he would have. Your goal is to make the Q&A the best resource possible for the topic - if a comment prompts you to do this, then get it done.
