Google posted that they have "restored access for many of those affected with Gmail bug, and that email was never lost." "Though it may take longer than we originally expected, we're making good progress and things should be back to normal for everyone soon."
So what caused this problem? Google says "We released a storage software update that introduced the unexpected bug, which caused 0.02% of Gmail users to temporarily lose access to their email. When we discovered the problem, we immediately stopped the deployment of the new software and reverted to the old version.
As always, we'll post a detailed incident report outlining what happened to the Apps Status Dashboard, as well as the corrective actions we're taking to help prevent it from occurring again. If you were affected by this issue, it's important to note that email sent to you between 6:00 PM PST on February 27 and 2:00 PM PST on February 28 was likely not delivered to your mailbox, and the senders would have received a notification that their messages weren't delivered," stated Google.