-
That's why my guess would be they found it via an unobscured URL in a PowerPoint presentation or on an ex-Sky laptop or similar.
You can get access to any TP activity as long as you know the link to it, but the links are made up of 26 base-36 characters (e.g. trainingpeaks.com/av/IQ7PABAD7CPABCDIBFLIQXB34Q - made up link, no point following it). That's roughly 2^135 possible links so the chance of finding any activity by plugging in random characters is very low, the chance of finding Froome's activities is staggeringly low.
Most of the other possibilities I can think of would mean they have access to all of his data (or all of TP's data) which is very unlikely or they've been holding on to it for ages and only just now decided to do something with it (again, unlikely).
And did they really only get the data from one stage? Or just the one stage where the heart rate looked odd? And is there a theory about what kind of doping affects the heart rate in that way? Etc, etc, etc.