Two things to remember:
1 - You get one cross-class slot for every 5 levels you have and being on a job halves that number.
2 - Slots are unlocked left to right.

You are synched down to level 24, which means you'd have 4 cross-class slots, being on Scholar means you'd have half that, so 2 slots. They unlock left-to-right which means that only the two leftmost slots would be unlocked, that means that Protect is probably on the third, fourth or fifth slot