And they're not detected in the sense that they realize, "OK, you must have changed my answer," it was more the case that, "OK, I must've misunderstood the question the first time I read it.
Die, die ihn entdeckten, sagten nicht etwa: "Sie müssen die Antwort geändert haben", sondern eher: "Ich muss die Frage beim ersten Mal missverstanden haben.