On my iPad (app) I have the following comment in my inbox.
I tapped on it and it took me to the question. I looked several times but can't find the comment. Then, I went to the site through my browser and the comment is not in my inbox there. Also, I have not answered or commented on that question.
Any ideas on this? I'm confused.
The answer to which the comment belongs was deleted. You don't have enough reputation to see deleted answers yet, so you don't see the answer, or its comments, when you visit the question.
But the notification system still shows you comments directed at you which were written before the answer was deleted. This is why you got it in your inbox.
This is what a moderator sees when opening the question:
At some reputation level (I think 10 000) you will be able to see deleted posts too. I don't think you'll be able to see the flag history to the left without becoming a moderator.
See also this explanation of visibility of comments on deleted answers.
