What I don't get is how people didn't notice during the group rides. I've ridden a few times with former athletes, and there was no mistaking the difference between an amateur like me and a former pro..
It's actually a similar story (minus the fraud): my local Trek dealership [in Budapest, Hungary, when I live there] had a few salesman who were former professional (tri)athletes, one of them was the hungarian national triathlon champion in his youth days. Some of the other guys working there were former mechanics for teams.
When we went for group rides, there was no mistaking their performance. The former national champion (sub-9 IM times)---although he wasn't actively training---was leading the pack, maintaining a 40+ km/h pace in strong headwind, veins popping on his legs. After a crazy 100km ride he took us for a run and was dishing out a sub-4:30 pace for "good training". You can't make that up.
Also, sometimes (very rarely) he'd still go to races and finish with very impressive times, often/usually winning his age group (eg. 40-45). He said he doesn't like going to races anymore, because his competitive side is crazy strong, and it bothers him if somebody is faster than him, even if they're younger. He had a very different, very competitive mentality compared to non-pro amateurs. An amateur, even soneone who trains very hard to get good times / PBs, usually isn't bothered by poeple being faster, because as an amateur that's always the case (pros are always way faster).