Excellent point Open!
There is a simple solution... since Discover says you didn't use your card to pay for the Discover Deals purchase and it is clearly on your account, then tell them they need to refund you 100% of the $540 since it's not a valid charge. Easy! 
@dwz55 wrote:Discover is taking longer to pay out on DD's cause of the possibilty of a person returning the item and keeping the DD cashback. I order stuff from Home depo tand Sears all the time and it used to take 3 to 5 days for them to acknowledge I went through the portal, now its been taking 2 months before they send an email.
As a data point, here's a timeline of my most recent Discover Deals transaction. It basically took about a month to receive a finalized email confirmation of the DD payout.
Fri 10/23/15 7:40 PM -> I made a purchase from LivingSocial after clicking through from Discover Deals.
Tue 10/27/15 11:00 PM -> Received 1st email from Discover confirming Discover Deals click-through activity.
Thu 11/26/15 5:05 AM -> Received 2nd email from Discover confirming Discover Deals payout amount (will appear on next statement).
My next statement cuts on 12/24/15, which means about 2 months from purchase until Discover Deals payout (could be as fast as 1 month depending on when your statement cuts after receiving the Discover Deals payout email confirmation). Not too shabby at all! 
Maybe we are spoiled from the good old days of ShopDiscover! 
I just wish that Discover made it easier to keep track of the credits like other online shopping cash back portals do.