Yes, the Lay of Aotrou and Itroun was where the phrase was in. Thanks for clarifying that. But there is one more reason that I think Tolkien conciously shuffled through old notes. If you read the whole lay, you'd know that only these two sentences bear resemblance to LOTR, and they happen to be STUCK TOGETHER. I think it would be too much of a coincidence to unconciously use two sentences that are right next to each other.
Yes, I admit that it would be hard to sue someone for Self-plagiarism
