I'm seeing them RDU-BZE and RDU-SJO, but when I try to go find available dates, it's telling me they've changed. I came here to see if anyone had found that.
Yahoo data comes from Travelocity, so it would have been a problem with the fares on the Sabre network. It's equally as likely some airline screwed up and posted $0 fares or Sabre got a bad feed for all the Central American destinations from someone.