If you are talking about the Mail app, the feature is still there. If you have not done so, try the common fixes listed below and see if it comes back. Also, if you are jailbroken, make sure you check any of your mail tweaks.
Besides entering the initial, once you tap the Bcc field a plus (+) icon should show up to the right of the entry field. This will pop up a small, searchable list of contacts.
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When you have problems with an app it's a good idea to clear it from RAM.
Close/Clear the app: With the problem app closed, double tap on the Home button to get the multitask bar. Tap and hold on any icon in the bar until they jiggle, then tap the minus sign on the problem app. This will remove it from RAM and insure a clean start the next time you launch the app.
If that does not work try a restart,
Restart: Hold down the power button until the power off slider appears. Slide it off. When the iPad finishes shutting down, hold down the power button again until the Apple logo appears. Apple recommends you restart the iPad at least once a month.
and then a reset if that does not work.
Reset: Hold down the power and home buttons until the Apple logo appears. The iPad will reboot. This usually takes a bit longer than a restart.