As a client, this happened to me a couple of years ago with a provider at her incall (her home). I took off work early on both occassions, showed up on time, no answer at the door and no answer on my calls. She was hot and I was horned up for her and that was why I was dumb enough to try a second time.
Lux makes a good point about setting up an incall just prior to the meeting.
NCNS goes both ways (client or provider) and its just as rude both ways.