Lars Sivertsen Austad

I am looking for information about my great uncle (Lars Sivertsen Austad). He left the Røra, Nord-Trondelag area in 1906. Arrived in the US via port Sault Ste Marie, Michigan on 24 Apr 1906. He emigrated to the US from St John, Canada, on the Canadian Pacific Railway, and seemed to have settled in Seattle, Washington. He applied for US citizenship on 2 Nov 1908, in Seattle. Then, on 9 Sep 1918, he rescinded his Declaration, saying that he expected to return to Norway, however the family never heard from him again. It is not certain that he did return to Norway. He was to inherit the family farm, but because he had disappeared, a younger son farmed the land. I cannot find him in US censuses - I have only his Declaration of Intention. Can anyone help? Thank you very much! Lucia Hansen