How did I not think of this sooner? I've always got several annoying pieces of 2"x3" card stock in my bag with my doctor, dentist, or beauty appointments.
One day, I'll have the time and memory to input appointments into my calendar the second I make a new one, but until now, it's appointment card city for me.
There had to be a better way — and there is! The answer was also inside my bag. From now on, I'm taking photos with my iPhone's camera of all my appointment cards. From there, I'll either email them from my camera roll, or just leave them there, because unlike a piece of flimsy paper, I know where to find it!