There are no specific airline code entry requirements for this functionality, but I am considering introducing some interface changes to make retrieving such fares more intuitive...
What were your input parameters? Did you turn on the "One Way" flag, by any chance (RTW fares are R/T)?
Oh, yes the One Way box was checked. I didn't even notice because I guess it was checked from prior use or something as I didn't click it when doing the search.
Thanks.