Well, this happened to me too, just now. And whats worse I did not even have any backup of my contacts(don't ask why). So what I managed to do is hack my way back to my contacts through Viber! 🙂
Viber app uploads your contacts to their servers and it stays there in case you install it on some other phone/platform.
So what I did is install Viber on a Windows PC (Probably would work very simillar on Mac).
I then went to:
C:\Documents and Settings\<MY USERNAME>\Application Data\ViberPC\<MY PHONE NUMBER>\
(Note: Application Data folder is hidden by Windows defaults. You need to enable: Show hidden files and folders in Tools > Folder Options > View)
In that folder there is a file named:
viber.db
Which is actually a sqlite database. I then went to:
http://www.sqlite.org/download.html
And I downloaded: sqlite-shell-win32-x86-3071700.zip (That is the latest precompiled binary for Windows that was there). I've unzipped it and I copied viber.db in the same folder. Then I launched the command line (Start > Run > cmd) and navigated to that folder. Then typed the following:
sqlite3.exe viber.db
And once it started, I've entered the following SQL query to get the contacts:
SELECT ContactRelation.Number, Contact.FirstName, Contact.SecondName FROM Contact INNER JOIN ContactRelation ON Contact.ContactID = ContactRelation.ContactID ORDER BY Contact.FirstName;
I hope this helps someone! As I know very well how frustrating it can be to loose all your contacts.