If you were logged into MySouthwest when the purchase was made, why not look there for the confirmation number?
I've never had to ask Reservations to find a confirmation number via my RR member number, so I don't know if it was once possible.
I think WN's systems aren't programmed to track reservations by RR number. This is evidenced by the fact that itineraries you purchase for other people while logged into
your MySouthwest account are not visible in
their MySouthwest accounts.
Also, thank you,
skoker.