The very fact that you've posted it will draw attention to the question and answer.
Any new answer (along with any edits to the question or existing answer) will bump the question up to the top of the "active" list. People will see it and they can get to it easily by clicking the "answered" link rather than the question title.
Other than that, you really don't have anything to do... nor should you, provided the existing answer isn't outright wrong. In that case, you're more than welcome to comment on the existing answer to clarify the parts you think are incorrect - which you already seem to have done.
Also, it's a bit unfair to say that the OP doesn't seem to care, considering they haven't been on SO in two days, so they probably haven't even seen your answer.
I suppose that, if you have some reputation you're willing to waste, you could open a "current answers are outdated" or "improve details" bounty but this (to me) seems a bit self serving. As it stands, the question has pretty low overall votes for both question and answer.