I've been through this with a VA flight that was rebooked onto NZ.
It is VERY difficult to get ORC on a partner flight not booked through DL. Essentially, you will have to get the ticketing airline to push ORC to DL, which they won't know how to do or won't want to do.
In your case, you'll need to appeal to AM to push ORC to Delta, essentially telling DL that you flew the flight even though you didn't. Because this costs AM money, and possibly they don't even know how, they won't want to do it. AM will say talk to DL about Skymiles problems, DL will say that they can't post miles for a AM flight, it has to be in initiated by AM (DL is right).
Additionally, not all airlines have a policy for ORC. In my case, VA said they don't do ORC in their own program so they won't do it in this case.
It took about 6 months and maybe 20 emails and phone calls to get my flight posted, and I was top status on VA, and they did it as the famous 'one time exception'. (I was crediting to DL because I already reached top VA status). So it is possible. But I say your chances are slim unless you really want to fight for it.