There is no evidence that those variables exist. A believer will work out a solution that they are comfortable with---with no way of verifying what they have decided is true---and they will move on to their next prayer. Will they conclude that it contradicted another more important prayer, that they have a lesson to learn, that a greater good is being accomplished? It doesn't really matter, they will be content with what they have decided. Remember, I used to believe in prayer, and not only JW style prayer, so I remember what my mind would do to hang onto belief. I did not 'lose' faith, as you put it, over prayer, but over evidence.
NC