The notifications for such things on the desktop browser version of Facebook are horribly broken, and clicking the link in the notification often does not go to the actual comment in question.
A solution I have found for this is to use the mobile version of the facebook website, as the notifications on that version of the site are far more accurate and clicking them actually does take you to the precise comment as mentioned in the notification.
To access the mobile version of Facebook, you don't actually need to be using a mobile device, you just need to click the following URL http://m.facebook.com then just click the notifications icon at the top of the screen, to access the notifications.