If this is a "SECRET" it's obviously we will never known it I would say at latest...
Personally I don't think there is anything like this. Make similar activity would requires TONS of people involved, strange bank movement and so on.
Yes even if they are using "SECRET" method of payment like bitcoin I would not expect nothing.
No one should have such interest in my opinion, at least at higher level. Something different maybe for a single team or player...