Something similar happened to me a few months ago.
I called to ticket the booking (an IB leg and a CX F one) 23 hours after it was put on hold
Everything was ok, I gave my card and account number and it went to ticketing.
A few hours later I check the reservation and the CX leg was gone ...
Apparently CX only lets partners hold awards for 24hours, even though AA says it's 5 days
My booking went to ticket on the hour 23 and some minutes and while AA was ticketing it, it vanished
Of course it was "my fault" and no compensation or real alternative was provided (they offered a CX Y seat for the same amount of miles )