sorry to hear this... but as many FTers will tell you, award inventory is based on the airline that you plan to redeem the miles through. For instance, AS may have 5 award seats available for their members (viewable on their website), but only offer AA 3 of those seats. It makes sense for programs to take care of their own loyalty members first and then offer the inventory for partners. These are complex partner relationships with many nuances.
In the future, I'd suggest calling AA first on the phone and confirming with an agent that the inventory on the partner is available for use with AA miles. Put that itinerary on hold and THEN transfer your points and issue the tickets.
Keep checking back with AA as inventory changes frequently.
I wish that AA had an online tool for checking availability of partner awards.