That's what I would do--

Write a nice letter with your ticket number, seat number, and day of travel and fax it to them and ask for credit.

Can't hurt.

They routinely update my account when I am 120.20'd or a flight cancels or doesn't post just by asking them.

MEM-ORD-PHL is like my own personal double miles machine, the last flight of the day almost never goes, they 120.20 me to the NW direct flight (I'm gold on them this has happened so often) and I get the UA miles too.

All with a fax.