I should be careful what I right here, but many years ago I was holidaying in the south of France and passing through a tiny airport that only services 5 airlines.
Low and behold, an infamous French steeplechaser was also passing through. This would have been near the start of his senior career, not yet a World or Olympic medalist, not well known, but I knew who he was.
I text my friend, a coach with the French Federation, excitedly sharing I was stalking him and a training partner in the airport.
"He should not be there" my friend messaged, "he is down as being in a training camp elsewhere" (I cannot remember where he said) He went on to say that there were rumours of certain athletes training at a mountainous region nearby, under the radar, an area the testers basically don't go to because it is remote, and that there were whisperings within the federation a lot of doping was going on. But he was registered at another training camp with the federation.
Said athlete then went on to smash his PB and win an Olympic medal. Oh, and punch a few fellow competitors, assault a mascot etc. in a 'roid rage.
I guess it's not surprising, knowing who it is, but the incident always stuck with me and the French Federation never did anything about the dodgy training camp.