A very similar thing happened to me once. I threw out a suggestion for a play date/meet up, and my friend's response to the suggestion was to show up at the time and place I proposed. Except I hadn't heard back from him, and figured he wasn't interested or available, and put it out of my head. But then when I wasn't where/when he thought I would be, he was mad and his kid was disappointed. Well, it would have been nice for me to get a phone call back saying, "Yes, we'll be there."
So, yes, I think you were right. You tried several times to confirm, and she didn't respond. The only thing I think you might have done in addition was to call her once more, that afternoon, to say "Hey, bummer that we haven't been able to connect but since I haven't heard from you, we're going to stay put. Hopefully we can work something out next time."