Gmail Gets a Contacts Restore Safety Net
The feature allows you to revert your contacts up to 30 days in the past. There are additional time points as well: 10 minutes ago, 1 hour ago, yesterday, and one week ago. There is also a custom setting, meaning you should be able to retrieve your contacts as long as the mistake isn't more than 30 daays in the past.
It's sort of like System Restore for Windows in the cloud. Of course, as with any cloud-based service, it will take some time to roll out to everyone. If you don't see it in your Contacts area under More Actions right away, be patient.