Looks like what they did was issue you a paper ticket for standing by on the Northwest flight when booked on CO. This happened to me earlier in April of this year when I was booked on a CO ticket going BNA-IAH-HNL and stood by for BNA-MSP-HNL on NW instead. The flights posted as Q (aka, "Pending Internal Processing," aka PIP), but were resolved about a week later. It's the paper ticket part that takes a while for the miles to post, but your patience might earn you 150% EQM on that flight.

aloha