Local contact folders disappeared

I did not sync my em client with Gmail. So I had one local Contacts folder. The computer was a new one and the few contacts inside came from the previous computer.
I worked a while building a distribution list, but I did nothing special. Nor I installed or run cleaning tools.

The result was that this morning the contact folder was empty and the email addresses that normally appear while typing disappeared, too.

Thank you

Unfortunate. One thing you could try is to close eM Client and run
C:\Program Files (x86)\eM Client\DbRepair.exe

When syncing with Google Contacts, if you lose locally cached data, you can just re-sync. Even if you delete contacts and they are removed from the server, it is possible to restore them through the web interface. But with local folders, you have no recourse unless you have a backup. So, a good policy when using local folders, is to have regular backups.