Comment 37 for bug 812394

While I agree that re-enabling hibernate should probably be more visible, that's a separate bug that probably won't be fixed for Ubuntu 12.04.

There is a help page in the default pre-installed help entitled "How do I hibernate my computer?" that explains how to test if hibernate works and how to re-enable it manually.

One reason why the bug is unlikely to be fixed is that it would require a User Interface Freeze Exception, which would require a Docs Freeze Exception and the translators are nearly out of time to translate Ubuntu 12.04 before release as it is.