Flagging a comment wont cause it to be removed.
Adding a reason behind your ID or even text suggesting what you feel something is is a perfectly acceptable use of comments.
That being said, other users can delete comments they did not enter (sorry, I dont know if only curators can do this or all users), and you will receive no notification that your comment was deleted. I don’t believe there is any way to trace who may have deleted it.
This ability to delete content has been raised as an issue. On the one hand if people put truly offensive stuff in, there should be a facility to remove it. On the other hand, it can be abused as was potentially done here.