Interesting, that's weird, that other site says:
ICAO K13S
IATA 13S
Either way, geonames always wants the ICAO, or 4 letters so you have to enter the K either way to ID the country.
As for an email, try info@geonames.org, I'm not sure if you'll get an answer though. Unfortunately, they're the only ones I have been able to find that has an XML/JSON service I can "talk" to.