Developer reply by Josh Geenen
Rated 1 out of 5 stars
Unhappy with the flakiness of Google Contacts add-on, I thought I'd try this. It wiped out my entire contact list not just locally, but in my Google account. Thanks
This review is for a previous version of the add-on (0.3.4).gContactSync will ask you for permission before deleting more than 5 contacts. If you're sure gContactSync did it I suggest you read dialogs more carefully in the future. Otherwise it's possible whatever else you are synchronizing your contacts with deleted them. Without more information I'm afraid I cannot help.
Google does have a very nice restoration feature inside Gmail if you view your contacts. gContactSync also makes backups but they aren't as easy to restore.
To create your own collections, you must have a Mozilla Add-ons account.