It depends on how the job was done in the first place, of course. Were fake memories implanted? Or are chunks just missing? Fake memories... that's really on the gray side. Not to mention, it's impractical. The kinds of details you'd have to recreate, the amount of time it would take to do properly, let alone aligning it into a the timeline of a person's life? Or it could be done really neatly, like Fairy Queen neatly, making it so that you don't even know you'd forgotten.