Another factoid. The alleged sample was a "B" sample. According to WADA rules, if the "A" sample tests negative, the "B" sample is to be destroyed after a certain amount of time. I don't know what the specified time is, I need to check my references on drug control. Of course the half life of the substances in question come into play here.
If I understand you correctly,the EPO would be detectable only if recently added to the sample,or at least the suspicion of that would be reasonable.
A deliberately doctored sample?