I recently had a similar situation with booking an AA award with a biz leg on Royal Jordanian. The RJ flight got discontinued so they automatically gave me a date 1 day earlier (without asking me, or telling me...fortunately i recheck my reservation every so often and caught it), but the departure on that segment was before my initial departure from my first city so it was impossible for me to make that flight.
I called AA and they said they would request from RJ to open up space on a flight at a different time. (there was no award space available when they requested it, only paid ticket space) I gave it 24 hours and rechecked online to see the word waitlisted next to my segment. I checked back another 24 hours later and it said confirmed. It worked out for me.