I can't help with your issue, but I will suggest that in the future you back up your contacts via Contacts > File > Export > Contacts Archive which will leave a restorable file in your documents folder. Although I don't need the information now, it would be good to know. If I need to restore my contacts in the future, am I correct in assuming that I go to the File menu in Contacts and click Import, and then select the archive that I had previously made?
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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