Yahoo: John Lithgow's disappointed face at the Oscars became an instant meme
Reginald Skulinski Eating or Reginald Skulinski Disappointed, also known as Monster House Stare Meme refers to memes based on a scene from the 2006 animate ...
The difference between "in", "by", and "with" in this context actually depends on the nature or type of disappointment you feel: "Disappointed with" implies that the cause of the disappointment was something basic about the nature or attributes of the thing: I was disappointed with my new toaster. It really didn't toast the bread as well as I hoped. The "with" form is usually used with ...
grammar - Is it disappointed with, in, or by? - English Language ...
Both "disappointed in" and "disappointed at" are idiomatic in American English. In general in American English, people tend to use "disappointed in" with reference to a specific person or group of people.
Of the list you provide, "in" is the most idiomatic, but there's also "disappointed by ", "disappointed with ", and "disappointed at " a person or persons. You can, apparently, be "disappointed of " some expected result, which can include the actions of some person. However, to me this sounds formal and somewhat archaic, and I would never use use it. As far as I know, "disappointed from " is ...
If one thinks "disappointed" must be accompanied by at least some tinge of dejection, the lawyer's phrase "agreeably disappointed" will seem oxymoronic -- or the word "agreeably" itself will have to be twisted to mean "not too disagreeably" as you have done with "not too torn up about it".