Physics Research help needed for a novel, about the moon rotating suddenly on its axis..?

Your scenario is virtually impossible. Some outside force would have to hit the moon to change its rotation, namely a large rouge moon of similar size that would no doubt ter enough debris to completely wipe out life on earth as a result. The earth is not tidally locked to the moon, by the way, just the moon to the earth. And if the moon began rotating somehow, it would take an equal force to stop it from rotating again so that the far side became tidally locked instead.