So it sounds like you were victims of "AutoReaccom". That is meant to rebook people when they won't make it. However, I have heard instances were something is calculated wrong and it makes it look in the system like you won't get it in time to make it, so it automatically runs and rebooks you. Then, you of course show up because the system was incorrect and you did make it. That, or the agents dropped you themselves by mistake. Which is also possible.

Although pretty rare, that does happen. And as far as I know, if that happens, the agents working that flight wouldn't have had any idea you were dropped. If you did make it in-time, then I do think they should have put you back on... but I am not sure of the reason or status with the standby's you mentioned. Hard to say.

Unlikely you will get any IDB comp, since it sounds like you were no longer booked on it. But they should give you something that's for sure!