Protection can be done one of two ways...

(1) "EasyRebook," which puts you on the next available flight (re: has Y inventory) -- note that EasyRebook has its limitations (if the next available seat to LHR is two days later, it won't rebook you; nor can it handle complex itineraries) and has been known to rebook passengers SAN-SFO-NRT to SAN-ORD-NRT.

(2) manually, which is when an agent "sells" your new flights & calls in for your ticket to be exchanged. If you were unprotected, that means an agent likely removed you from the flights (why, I don't know) -- unless EasyRebook put you on the 6AM, the agent on the 10AM and AutoRobot killed the later flights for duplicate bookings -- not likely to happen within 24 hours.