Hello,
As you have still Book it! 1.5.9, I have to informa you about different topic:
TOPIC: Warning Message after Upgrade to 1.6.0
Book it! 1.6.0 is not compatible with Joomla 2.5. So do not upgrade, or you can get Book it! 2 for free and contact us on email. More information in that topic.
To your problem:
You should add link to menu Customer reservations list. Customers will be able to check their reservations there and also allow them some modifications. They have also chance there to pay it again if first payment fail.
Reservation detail can be opened after click on reservation number.