Your PWYW voucher discounted 100% of the normal fee for eligible services, so you likely skipped the payment page all together. (Nice job!) Here is how Pay-What-You-Wish works:

• Step One: Come to your appointment! If for some reason you find you can’t make it, please reschedule or cancel in accordance with our policies; even though you have nothing to lose, we are saving time for you and would prefer to be informed in advance if that should change.
• Step Two: After your appointment, you will receive a follow-up email that explains the rest. You will find a link to our Paypal Tip Jar and an earnest plea for your valuable feedback. If you’ve been offered this voucher, we probably need your feedback just as much or more than your payment, so please do take the time to let us know how it went – the good, the bad, and the ugly!
• Step Three: Tell your friends to give us a try!