You should have received an order confirmation email titled ‘Your MP3 purchase from Myxer, Inc.’. There is a link at the bottom of the email that you can click on to download the mp3 again.
Look for: If you were not able to complete your downloads, they are available here.
Just click on ‘available here’.
If you still have trouble, please contact customer support at email@example.com. Include a description of your issue and your order number in your e-mail.