Pretty sure NW orders their standby list by mishandled pax then elites then everyone else. In theory you should have been higher on the list than the two silvers. Fare class (except full "Y") doesn't play into standby as far as I know.

I'm *guessing* that you didn't get the seats because you said there were three of you flying. Your original post implies that only two seats were available. If that's the case, you were probably overlooked by the GA and the seats given to the next two guys on the list. Just a guess.

-RM