If the question was on topic, then your work doesn't have to be wasted. Just create a new question about the topic yourself and self-answer it. (If you can still access to your own answer, but I think that should be possible)

> Why bother answering, when answers must be accepted by the poster and poster does not even know they should accept an answer in the end?

There is no obligation to accept answers. Often the accepted answer isn't the best answer anyway.