I would definitely be enraged if this was going on in my seat, and I wonder if it had, if I would have been able to track this down and figure it out. True, I have way too much free time. But even if one is hiding their schedule, you can pull up a trip and figure out what is happening. Who picked it up initially, were they in the air at the time, who ended up on this trip, did it disappear and go into sub.
I can actually understand how someone could get away with doing this consistently time and time again, with a group of friends, in a way that is legal and by the contract (though sneaky and a lot of work). Any additional heads up by a scheduler would be a bonus. I'm not going to say how, don't want to give wolf pack wannabe's any new ideas. If this is a flaw in the system, it would benefit both the company and union to get rid of it. Honestly, for the company, this should be easy to track, if they desired to do so (which seems unlikely).