Something is missing from the story:
flight arrives EARLY to MIA according to Mom
Dad was at the airport but didn't have his gate pass yet
an HOUR after flight landed early, AA calls Mom

Seems unlikely the daughter was wandering around for an HOUR
What seems MORE likely is the daughter didn't obey instructions to remain seated, and walked past FA's who waved her off/waved goodbye
daughter reunites with DAD. Didn't call Mom to say ... Mom what do I do
Neither daughter nor Dad updates anyone from AA, so they assume she's missing

I will bet you a boat load of FF miles that the call to say "we lost your daughter" came AFTER Dad was on phone with daughter.

unfortunate events,
Call me jaded, but "mama" is tiktok famous now