Have them forward you the email receipt. There is a download link in that receipt, and it should also have their license code.
If they didn’t get the email, have them check their spam/junk filter. They can also login to their user account here on the site and click on the “Purchase History & Licenses” link in the upper right corner (must be logged in first), and then they can view their receipt and download link + license code.
If none of that works, send me a private email via the contact form, and I’ll send you a direct download link from their purchase.