During the surprise test, they took 2 samples. They test the first sample purely for T:E ratio. This does not tell if there are any steroids in the system, but if the T ratio is high then it's a pretty clear indicator that they are on test or roids.
The second sample is reserved for the athlete to request to be retested if they believe the first was incorrect. If the second same is tested they actually test for the substances not just T:E levels.
Overeem and camp never requested to have the second sample tested.