So you went via AKL?
Great Circle Mapper
Does look like AA made a mistake. They should have ticketed you to get back home
Did you pay for NAN-xxxx-MSN?
As you flew a Star Alliance airline you can credit that to UA or whatever ffp.
And claim "
original routing credit" from AA for the flight not taken
Brave people not taking travel (medical) insurance. A medical event could have left you at worst penniless.