Yes I'm sorry too your plans were canceled because she had a date - that's not fair. Sorry this triggered you. I can never understand parents who don''t make the effort to shield their kids from them having sex. I would be so embarrassed for my children to know - yucky and weird for sure.
When plans don't work out for me, I think there's a greater reason things were canceled - like maybe God didn't want you to get in a bad accident. Do something nice for yourself - you can still go and look at the cello's or do something else? Don't let them ruin your day - make it a good day anyway ((Evening)).