I hate when life answers the question "why"
When I say "I'm coming" that means "I'm coming." It doesn't mean "I'm not coming." It doesn't mean, "Yeah, go ahead into town without me. Don't bother trying to let me know first. Don't bother answering your phone when I know you're there." I worked really hard to make sure I knew the time and place and even to be reachable in case that changed, and still nobody mentioned the time change. So now, having given up valuable work time and also skipped dinner to spend time with the people I care about, I'm left microwaving soup and stressing over what I could have gotten done instead of traipsing all over campus looking for people who didn't think I was worth telling when plans changed until afterwards.
I'm not sure what it means that near strangers seem to care so much more about me - greet me with smiles and hugs and even let me know when things are happening - but I know they don't really.
Edit: Apparently they did try to tell me about the change (albeit still afterwards). Also, I ended up with a much better and cheaper dinner than I would have had had I gone with them. And there was a loud scary startling noise that I'm glad to have missed. All in all, I guess it worked out for the better.