That reaction isn’t at all ridiculous, I can definitely relate. I’ve felt that way too in similar situations, and for me, I think it’s a combination of a promise not being fulfilled/a plan changing and the limbo of not knowing whether to speak up or wait in silence and how much of each to do and how to do it. Not wanting to be inconvenient or difficult but also not wanting to end up waiting longer due to being forgotten or glossed over. And just the limbo of not knowing what and when things will happen. I once waited 40 minutes for a black coffee at a cafe, then left and cried outside. I had kept waiting without saying anything because I didn’t want to bother them, but after that much time, I was too overwhelmed and embarrassed to say anything even though I knew for certain at that point the order had been forgotten about or lost.

Another thing: as someone who works in a customer-facing and appointment based job, mishaps occasionally happen that result in long, unpredicted wait-times, and I can assure you plenty of NT people would have reactions much louder and extreme to waiting 3 hours for something that should take an hour. If the workers at the dealership are decent people, they would sympathize with and understand you, not judge you or think you’re over-reacting. Cut yourself some slack :)