In my notification bar at the top of the page, there's a pretty rude comment about my question, but when I try to look at it, it's already been deleted. I'd really like to be able to respond to that comment (in a polite, professional manner, of course.) Is there any way I can see comments that have been deleted?
No, there isn't. Moderators can see deleted comments, but regular users cannot.
Since the comment was deleted, I don't think there's any need to respond to it either. I would just let it go. No good can come from responding to someone who's just being rude, no matter how polite and professional you are in response.
Look on the bright side - the system works and the rude comment wasn't allowed to persist on the site.