I performed a factory reset on my Lenovo A390. I forgot to keep backups of my contacts, and I lost a .vcf file and my contacts are gone. I have important official documents and contacts. How to get that .vcf file back?
Sorry to say that but i think your contacts are lost forever...you can download an app that may scan your drive for deleted files and that may need an root on your phone and is not 100% guaranteed.
Very likely the space where your contacts were has been overwritten so is not possible to recover it. Next time keep an backup on your external SD card they are not deleted in factory reset and/or your PC or gmail account.
That is true for photos documents and all your data is lost forever if you do not have an backup.
If you want to try an app google for something like "recover deleted contacts android" that should point you to an app capable of that if there is any.