wibb,
When you deleted the "virus", you deleted the directory where it was located....Your Inbox.
Check the recycle bin to see if it appears there.
Also check the Avast Chest to ascertain if by chance you sent it there for quarantine.
If it does not appear in either place, then as a last resort, you can try to access your email via webmail. Most ISPs have internet access. If you did not set Thunderbird to delete mail from the server after download, then the email may still be on the server.
otherwise.....it's all gone. Sorry.