OhioSpyderman is probably correct.At least read the thread and look at the pictures before you “guess” based on anecdotes about a Ford Focus.
Since the caliper is not frozen, there simply is no way for inner and outer pad to be so different.
And he was not saying the pad fell out, but that the friction material bonded to the metal pad backing plate, must have broken loose.
That actually happens easily and frequently.
The metal expands and contracts greatly with temp, while the bonded friction material does not.