Hi Mike,
It could be that the reservation was already confirmed - if you make a reservation within the confirmation window (which is set at 48 hours on your scheduler) it is automatically confirmed. You still get the confirmation email even if the slot is already confirmed - I probably need to work on the language in that email if the booking his already confirmed to avoid confusion.
If the booking was made more than 48 hours in the future let me know and I'll look through the code.
John Davis