Although Grover's algorithm is extremely impressive...it's a probabilistic algorithm, which means that the result is not guaranteed, but very likely. And the likelihood can be increased by running the algorithm more than once.
The likelihood increases exponentially because each time you run the algorithm it's independent of the previous times. Even if it's only 75% sure, you only need to run it a few dozen times before it's more likely for there to be a hardware fault in your display giving you the wrong answer.