Hi Sharon,
We have 3 Ruehter families living in our area. They are James and Bonnie Ruehter from Lexington, MO; E Ruehter and Bill Ruehter living in Higginsville. I don't know if they are related but it might be worth a try.
Have you looked in the passenger record books at a genealogy library?
The Lutherans kept very good records so it is possible that you can find him there.
Good Luck. Shirley