The few warforged that exist on Kitara are not so much a race as they are an accident (or achievement depending on your outlook). Warforged are golems created by wizards in a ritual that proved particularly successful (or unsuccessful as some would say). Rather than getting an obedient golem, the ritual actually created a fully sentient creature that was not beholden to its creator.
The cause of these “mistakes” is not understood by the sages of the land. Many have attempted to recreate warforged, but to date, there are no known cases in which someone was able to intentionally create a warforged. At present, it is believed that there are approximately 300 warforged on Kalamora.