Is it considered a sin to drink water from a paper on which a shaykh has written "scribbles and words I cannot read," claiming it to be for ruqyah, and also to wear an amulet, then burn it after learning of its prohibition, knowing that the reason for going to him was for legitimate ruqyah with the Qur'an?

So long as you went without knowing the reality of the person and what he wrote, we hope there is no sin upon you; for Allah Almighty says: "And there is no blame upon you for that in which you have erred, but [only for] what your hearts intended." You did well by burning the amulet, and you should advise your friend and warn her against going to him again.