You may contact avast via this form http://www.avast.com/contact-form.php
In the drop down menu click on “sales inquiries”
There is an outside chance your purchase has been logged.
If that is the reason use this form to re-send purchased license(s) http://www.avast.com/resend-license-paid.php
Make sure you use the same email as when you purchased.
I don’t work for avast so I can grant no guaranties.
But I hope this helps. Please keep us posted. 