You may want to check with the Red Cross to see if they have any post-war records. Germany did give some scholarships to survivors to pursue certain technical or educational tracks such as textiles so he may have stayed for practical reasons such as work or education. It wasn’t easy to get a visa to the US so many survivors weren’t able to immigrate. You may also want to contact the Jewish Museum in Frankfurt and the Jewish Community of Frankfurt jg-ffm.de. Someone may have known him or have interviewed him after the war to document his story. He may have been active in the synagogue or with the Jewish community in Frankfurt so some records may exist. He is listed in the USHMM’s database so maybe you will find documents from his arrival in Germany. Like many survivors he may have gone to a DP Camp after liberation. Best of luck with your search…
Lisa Malamud