Yup, I so wish things were old school. It takes the awkwardness out of situations.
I will say, however, that I feel sorry for the birthday girl. I mean if your friend said she was going to throw you a party and then dropped the ball like that, what would you do? I would feel compelled to see if anyone was actually attending and if there was, in fact, a tea party still in the works. She was put in the awkward position of following up. I would be so pissed at my friend.
ETA - Geri brings up another excellent point. The RSVP'ing to a party. I know when I have thrown a party I have felt almost compelled to call, and call, and call, because no one does it anymore and then when they do, they change their minds or have a change in plans and then they don't call and tell you that part and so you just never know. I have never done the phone stalking party planner thing, but man have I wanted to. Just another way we have forgotten out etiquette.