With these assumptions, then the 'sympathetic magic' thing would seem to increase the probability of the desired outcome occurring in at least a few such simulations, thus at least mildly increasing the probability that the person involved will experience the desired effect.

It would increase the probability of the outcome occurring in simulations in which the protagonist does not come up with the trick. (Or doesn't apply it to this occasion, as DanielLC mentions.) In simulations where the protagonist does come up with the trick (and applies it to this case), it's a sufficient explanation for the various notes which the protagonist leaves; the events don't need to happen. So leaving false notes will only have the desired effect in simulations in which the protagonist is sufficiently different so as to not leave those notes.

This could still be worthwhile to the protagonist.

For fun fiction, such a simulated protagonist could eventually understand the trick and what is happening. (The simulated protagonists actions would still have no supernatural correlation to other events in the simulation.)