i see.....well, if you had a compromise like doing a play or something similar, it was the right thing to do.
If the punishment was to choose between drama forever and ever and prom. You did the best for the long term (if you enjoy drama club).
Try to not think about what you are not having tonight and focus on enjoying what you have. I remember having lots of fun at improv classes. Because if you keep thinking about what you missed, you will not enjoy this day.
Wish you the best!,
Ps: you can have prom the next year, right?