From how I described it, it certainly sounds like a case of something else bothering her that just spills over into other, unrelated things.
But, for what it's worth, that's not really how I experienced it. She seemed perfectly upbeat and untroubled both directly before and directly after the hanger hangup, judging from her interactions with the dogs (which have a tendency to be rather telling when she's in a foul mood).
I got home fairly late (just before 11), which I was expecting to get some flak for, as she sometimes decides to go to bed earlier than 1 AM and doesn't appreciate my being awake and disruptive to her sleep patterns on those occasions... So there might have been some of that involved, but normally that just gets directly mentioned rather than putting a shadow over something else.
It's not the first time I've been given sudden shit for having done/not having done something, and then caused a fluster by pointing out that it didn't be like it do. I've been griped at before for clogging the kitchen sink and blocking it up, after she accidentally pushed the drain toggle. Her standard apology for these cases of mistaken blame is to just never mention the incident again due to the awkwardness of having to admit an overreaction.
RE: Alacrity. I have no shame in admitting that I was introduced to the word by Baldur's Gate 2... It's a fun word.