alas: "If you purchase a ticket on a flight that is marketed by United but operated by another airline (known as a code-share flight), the operating airline determines how many miles you earn for your flight." http://www.united.com/page/article/0,8566,3122,00.html

OTOH: "Note that the booking class that appears on your ticket may differ from the booking class that the operating airline uses to determine flight miles earned."

i've never been sure if the fare code that's listed is the UA fare code or the codeshare operator's fare code. you may be able to call SN and ask them what it was booked in -- maybe it did end up in something better? (though i wouldn't hold my breath, since it looks like most cheap economy gets 50% :\ )

jon