I wonder how anyone can know for certain that any specific sign came from the Lord or from some other source. Don't the evil spirits have power to produce signs as well? For example, I know a person who said, if that man shakes my hand, I will know he is a servant of the Lord, and then the man unexpectedly went out of his way to shake the person's hand and no one else's, and so the person and many others all took it as a sign that the man was truly a servant of the Lord. But what limits only the Lord to whispering to the man that he ought to shake the person's hand? Wouldn't it be equally as possible for an evil spirit to do so? And since the person is looking for a certain sign, wouldn't that be motivation for an evil spirit to try in order to mislead the person?
The same questions could be applied to the subject of the OP. What precautions were taken to make sure that his thoughts and prayers were received by the Lord and no one else? How can he be certain that when he receives his code, it's truly the Lord giving him the code and not some dark entity desiring to lead him astray?
Now that I've asked these questions, I would say that this world is full of signs from the Lord sending you messages about what you ought to understand. Are your children disobedient? Are you angry at your spouse? Are you unable to keep a garden growing? Do the people around you all seem to have the same flaw? Do they all stab you in the back on a regular basis? Or do they tend to be hypocrites? These are all signs given to you for your benefit so that you can see the weaknesses in yourself and turn to the Lord.
When you are looking for signs solely for the purpose of repenting and becoming more like the Lord, in a state of humility, then interference from the dark side will have very little power over you. It will be easy to filter out the evil from the good because evil always prompts you not to repent, not to pray, not to forgive your loved ones. And good gently guides you to do those things every single time.
What did Alma say to Korihor when he asked for a sign? Thou hast had signs enough . . . I would say that sign seeking is wrong because if you need a sign, you are ignoring the plethora of signs all around you which are calling you to repentance and testifying of the Lord's love and goodness to his children. At least, that is what my experience suggests is true.
