I looked on ancestry.com for your grandfather Sielski and saw that you had researched there. But I wondered if you saw the following 1916 census listing for a Nicola Sielski, prisoner of the Royal Northwest Mounted Police in Medicine Hat? Since he had an Austrian passport, he may have been interned after the 1916 census was done in Humboldt, Saskatchewan. Have you ever heard anything of this? if so the Canadian government may have records. If you go to the following document in ancestry.com, you can view details.
1916 Canada Census of Manitoba, Saskatchewan, and Alberta
about Hykola Sielski
Name: Hykola Sielski
Gender: Male
Birthplace: Austria
Home in 1916: 16, Medicine Hat, Alberta
Address: 113, R N W M P
racial_or_tribal_origin: Austrian
Household Members: Name Age
Eric Colclaugh 21
Wilber Spraule 27
Dennis J Murphy 26
Leonard J Russell 23
George Kawolchick
Joseph Deweschuk
Peos Prasuk
John Kanolchuk
John Litwinchuk
Aniol Kauski
Hykola Sielski
Hy Xola Ilonski
In 2008 the Canadian governement set up a Canadian First World War Internment Recognition Fund:
Canadian First World War Internment Recognition Fund