In 1876 he was traveling and when the passengers realized he was on board, he was asked to sing a song. He wanted to sing a Christmas song, but was led to sing something different. You can read the whole story here.
You can also get a Kindle Edition of the life and the story of gospel hymns by Ira D. Sankey. I just purchased mine and I am looking forward to reading it.
My Life And The Story Of The Gospel Hymns And Of Sacred Songs And Solos (aff. link)