When a black belt spars, he or she does not think about sparring, it just happens, much the same as a experienced driver does not have to think about how to drive a car, the brain just does it automatically. If a person was ever a legitimate black belt, they will never forget what they learned, barring any mental problems. Even if they have not trained in decades, when asked, they are able to immediately step into a perfect back stance, since the motions are embedded in their procedural memory. Fraudulent black belts, instead of performing the stance properly, will make excuses about why they cannot remember how to do it.
Semantic memory is factual memory. These memories are relatively long lasting; in the case of Alzheimer patients, these will be the next to last memories to go. When semantic memories are based upon the truth, they last much longer. We use these memories every day in remembering where we parked the car, what year it is, or whether we ever earned a legitimate black belt. Illegitimate black belts have a difficult time remembering the dates they trained, their schools they trained in, what they had to perform at their black belt test, and other facts.