Dear Ms. Mansky,
Thank you for posting your request on History Hub!
Since he was held by the Russian Army, we suggest that you contact the Federal’naia arkhivnaia sluzhba Rossii (Rosarkhiv) [Federal Archival Service of Russia], ul. Il-inka 12, 103132 Moscow, Russia for any records they may have.
You may wish to review Archives of Hungary; National Archives of Hungary; Prisoners of War (Russian Empire); How POWs in Russian WWI camps faced a life or death lottery; Sretensk prisoner of war camp; How Did the Allies Treat Their Prisoners in World War One?; and Prisoners of the First World War websites for additional information and/or resources to assist your research.
We hope this is helpful. Best of luck with your family research!