Hey Deef
use that email address and send an email to them explaining your trouble.
The error just means you dont use a Email Program on your computer, so whatever you use for emails you will have to enter that address in manually
members@worldgolftour.com
Send them your issue, the name of the member who you gifted and accidently sold the clubs.
They will check both of your accounts, and they will reverse the sale your friend made back to the pro shop
Let me know how you go mate !