Currently Being ModeratedJun 7, 2013 7:27 PM (in response to nathalied)
Are you using Time Machine?
If so, you may wish to attempt to restore them from a recent backup. Restore this folder:
I would recommend you first export your current situation in case something else goes wrong, that way you could get back to what you have now. Then delete all your contacts, ensuring they're deleted on all your devices (including and especially iCloud.com). Disable iCloud Contacts. Restore from Time Machine. I would then recommend exporting those, just in case. Then reenable iCloud Contacts. It should upload your contacts without issue.
If you don't have a Time Machine backup, you may try restoring from an iPad or iPhone backup and syncing them back to your Mac, making sure to disable and reenable iCloud Contacts at the proper times.
If you have no backups at all, you're likely out of luck. Hopefully that's not the case. Hope that helps!