The trigger's controller needs to demonstrate awareness the first time it would have a visible effect.

And taking an illegal action beyond that point would indicate that the necessary awareness wasn't demonstrated.

Where it gets tricky - and I'll have to use the old “have to be there” cop out - is, if you back up to the point of the illegal action, is it no longer too late to demonstrate awareness? I think, in general, I'd have to be convinced that there's a good reason to allow remembering an already-forgotten trigger - but I won't say it can't happen.

d:^D