So only one jurisdiction? Hong Kong which operates a "closed system."
I assume you mean "pre-race test" - at what stage do you "pre-race test" before a race? One hour, one day, two days, three days, a week? It takes time to process the tests particularly to a degree that would be evidential.
The "event" that caused the positive in this latest case may have occurred any time after the "pre-race test".