Squirt, keep calling until you find out when she's working again.
Make another appointment to see her. Ask for the same massage, however, don't tip anything up front.
At the end of this massage, give her what you feel she deserves for both sessions (minus what you've already paid, of course).
Al Cohol
If you have a buddy who can come with you and wait in the lounge in case of some backroom boys, that'd be a safe idea, too.