Thank you. I looked up the details about Marty Nystrom composing "As the Deer" and couldn't find anything like the story you told. He seems to have a full narration of the composition experience in the book "I Could Sing of Your Love Forever" by Lindsay Terry. He says he was on a retreat at a Christian organization in Dallas and set out to write a song on the piano.
So we see that you reached a conclusion about Mullins on the basis of a phantom memory about an unrelated singer. A perfect example of Evangelical processing of sexual information. A worthless process.