Anton Olufsen, arr N.Y. 18 May 1891

Hi all My great grandfather, Anton Olufsen left Christiania (Oslo) on 1 May 1891 on S/S Thingvalla which was scheduled to arrive at New York on 18 May 1891. His destination was Hendrum, Minnesota, and when he left Trondheim on 27 March 1891 the records state that his ticket was being paid in the US. 1. How would I go about finding out who paid his ticket? From what I can see so far he didn't have any family in the US. 2. It is said that Anton returned to Norway after 4 years, are there any records of the people who left the US? Thanks. Charlotte