As I think through this, I actually think it's far more likely AA changed the OPs ticket than CX.

Glad it worked out to the OP. But I think this thread is a showcase for how screwy the entire industry is. CX sent $100 (admittedly in a voucher that I probably would say is worth 50 cents on the dollar, so let's call it $50) to a passenger whose anger I'm pretty sure was mistakenly directed at the wrong airline!

My other conclusion is CX did a pretty solid job here. Bummer the first flight was delayed but everything else they did was a spot on job. Although I can't tell from the OP, it sounds like he/she was flying economy and doesn't have any CX status. Not bad! If only CX could direct some of that diligence to their catering in J and F....