There's no additional clues to the code, you have to figure out yourself. I actually did think of making them fail but then I thought that it may be too cruel and leave a foul taste in their mouths, especially if that's the only thing from stopping them from saving their parents. It could potentially sour the whole game experience, even if they had enjoyed it until that point.
I didn't think that it's too impossible to be honest, I've seen several videos where the people figure out the password without Miranda telling them about it. But if I do expand this game out, I probably would have difficulty options where Miranda could help solve several puzzles if you are stuck with on easier difficulties limited number of times and on harder difficulty, you'd have no safety net and would have to rely entirely on your own wits.