It entirely depends on how they rebooked you.

Others are assuming you were rebooked into the PerkPass fare class. That might be the case and since you are talking about DL my past experiences with NW might not have any bearing on this scenario. But I can tell you from numerous past experiences that when NW would make this kind of a screw up (the SIN office was notorious for failing to ticket) or allow rebooking due to national emergency (e.g., coup in Thailand), there were agents who would just book into revenue classes on NW metal. There are times where that is the easiest (or only) way to get the passenger promptly rebooked-- instead of calling inventory management and opening a seat in the appropriate class.

That said, even if that's what DL has done, I would venture a guess that your only benefit will be getting miles. Whenever we called in to subsequently modify any of these "revenue class" awards, the agents always caught that it was originally an award ticket. So when you call to upgrade, even if this is now booked as a "Y" class fare, the agents will likely figure out what happened. Worth a try though...