SGC kept my Vic Willis T206 gray back variation

[Mark17]

For the past few years I'd been looking for a Vic Willis T206 portrait with the gray back variation. This September I found and bought one on ebay from battersbox.

https://www.ebay.com/itm/194250670218

I wanted to send it to SGC to get it authenticated and in a slab, certain it would not get a numeric grade due to condition issues, but confident it would get an Authentic designation due to the reputation of the seller.

SGC, through my online order status and email, notified me they couldn't grade it, and refunded me the $30 for it. On the invoice I received with the rest of the order, next to the Vic Willis entry, it simply says "Cannot Grade".

Okay, if they don't want to grade it and they refunded the money, that's fine, but here's the problem:
THEY KEPT THE CARD!!

I just sent them a message that says:
"I just received my order, invoice #208604. You graded and returned 8 of my nine cards, and did not return the best one - the Vic Willis T206 gray back variation. The invoice says "Cannot Grade" due, I suppose, to the printing error that caused the gray background color. But you kept it instead of sending it back. This printing error is somewhat scarce and if you don't want to grade it, fine, but at least return it to me ungraded."

Is this a common thing??? I thought these guys were ethical.