I would have assumed "protected" meant you were booked on the flight (not waitlisted), but that doesn't necessarily mean you have a seat assignment.

What ended up happening? In the event of IRROPS, they're allowed to accommodate Super Elites on overbooked flights.

Anyway, this is exactly why they should allow free standby for earlier flights for anyone who wants it. I bet your original flight went out with empty seats, and other people got bumped on the later ones.