I emailed the email address and got a response!

Hello,

We're sorry you haven't received your free Greenies sample. Due to a high volume of sample requests the samples are taking a little longer to arrive than originally estimated. I did find your information on our fulfillment list. You should receive your sample shortly.

We apologize and thank you for your patience.

Have a great day!
I hope that answers some of your question who haven't received theirs' yet!