Okay, I can get that someone might be that level of shy...but...I cannot get that they didn't MAKE A FUCKING EFFORT. Social skills are like other skills; a lot of people do not have the natural aptitude (and some have disabilities that hamper their efforts) but you can tell when people are trying, and it's only by trying and getting experience that you are ever going to figure out how to pull the whole thing off. Saying 'thanks' and offering to cover your share of the tab is pretty basic stuff if you give half a fuck; this person does not even give one quarter of a fuck about how to treat people irl I guess.