I believe the sample is taken as soon as possible (dog-willing and needing to go) from immediately or up to 6 hours after the finish. We do not know when the samples were taken for this specific team -- but ITC and the volunteers and the vets should, and probably did, record that data. Over the years numerous volunteers have recorded their specific experiences of being on "pee patrol" at the finish line. ITC has not released the identity of the team or the time the samples were taken -- just that the substance was Tramadol and that "numerous" dogs in the same team had tested positive for Tramadol. That fact, by itself, does not prove when, where, how or by whom the substance was administered -- hence it is not possible for ITC to "charge" someone with an offense. See Mitch Seavey's comments.
My guess is that most of the top twenty mushers have a pretty good idea about which team was involved, and probably so does Craig Medred -- but "saying" what they think is prohibited by ITC rules and regulations and fairness. Private gossip is probably pretty accurate, but libel and slander is not nice.
ITC may have been painted into a corner, but it's probably a corner that they have built themselves. Openness and transparency in all matters would help, but that's not ITC's style.