Relaunch i-bank pass and select "My i-bank pass tickets" from the menu (≡). There, you will find the ticket you had generated, which you can show at the counter when your number is called.
Note that every ticket issued by i-bank pass remains active up to the moment it is called by the counter of the branch where you have chosen to be served. After this time the ticket is marked as invalid, whether or not you actually turned up.
Timed-out tickets are displayed too under "My i-bank pass tickets".
All i-bank pass tickets (active or timed-out/cancelled) that you have generated in the past are displayed here.