Are Oil Free Air Compressors REALLY Oil Free?

I have an upright 27 gal. Oil Free air compressor that was in the trailer that wrecked (another thread). When the wrecker crew cleaned everything up they laid the compressor down on the rollback and oil ran all over. They stood it up when they noticed, but where did the oil come from? I have been afraid to start it up to see if it still works because of that. What gives? All the documentation I can find says no oil. So where did it come from? Any help would be appreciated.