You've pretty much hit the nail on the head.
Commenting that you think you know the answer is fine.
Commenting with the answer is even better as you might get a response from OP to confirm it (in which case it's almost certainly going to get reopened and then you can convert your comment into an answer).
Voting to reopen is a key here (if you've got sufficient rep to earn that privilege) as it will then enter the reopen queue, to be reviewed by other users.
Editing "correct" information into the question is a big no-no because you might be thinking of a different, but highly similar property.
You could also, as you've done, raise a meta question.