Faldage has what would fit the closest for me, but I'll add 'disappointment' anyway.
Which leads me into thinking about expectations: things like this always seem worse when we have been expecting gratitude, or at the very least acknowledgement. Something, akin to assumptions I guess, that I've not been able to completely rid myself of yet. Even when long history would seem to warrant you being able to expect a certain behavior, people can still let you down--which of course wouldn't have happened if you had not had the expectation.