Steamship Etna

I have a copy of 3 pages of the manifest (from Vesterheim Genealogical Center) of the Steamship "Etna" that arrived in New York from Liverpool on July 6, 1868. My great grandparents and their children are listed. I can't find this ship and passengers on your website. Although everyone on the page (I have) is from Norway, in the column "the country to which they severally (sic) belong" is listed as Sweden. Technically, they belonged to Sweden in 1868. As they were not listed as Norwegian, is that why this ship and passengers are not listed in your records?