What if exogenous?

For sake of argument, assume that the B sample (and maybe the A) are deemed to have foreign (exogenous) testosterone present. Two questions come up, "What happens", and "what happened."

What happens seems clear enough -- Floyd is nailed, loses the title and 4 years from the ProTour, and likely ending his career on the road. Is there anything he can do in the interim, like return to MTB?

"What happened" is intriquing, but probably doesn't affect the outcome. The possibilities as I can speculate include:

1. Guilty, Guilty, Guilty.
2. Contamination during analysis (consipiracy of stupidity)
   
3. Contamination during transport (conspiracy of idiocy)
   
4. Contamination during testing (conspiracy of dunces)
   
5. Sabotage during or after testing (consipacy of evil theory)
   
6. Other party doing something unknownst before or during the stage.

I am curious about the last scenario. In what way could Floyd have been doped by someone else without knowing? Is there a way to spike food or drink to produce these results?

If there is a way, who could have done it, and why? We're left with ostensible "friends", competitors, and third-parties as possibilities. It seems to me that all of those classes probably figured he was dead after stage 16, so it is hard to imagine competitors or third-parties bothering with a sabotage in anticipation of stage 17. That leaves us wondering if a "friend" might have tried to "help." This is a disturbing line of thought.