I can certainly understand your frustration.
However, you said you were "pretty much counting on the card bouncing back if Jeray also scanned Jackson" which is totally not written in the rules. So, you know, to some degree you dug your own grave.
I mean, what would you have done if Tamius had immediately responded with: "You can't use it on Jackson. Either choose a different target or don't play it, in which case I will publically state you chose not to play your card"?
I'm sorry you ended up on the wrong end of this, but if we had allowed this to stand and the Spies would have won, then the Resistance would now be complaining that you won by cheating.
Just because a case isn't specifically defined in the rules doesn't mean that anything goes for it. To go for a slightly ridiculous and hyperbolic example, the rules don't say that nothing special happens when someone mentions pandas. They don't have to because if something like that isn't mentioned by the rules, we can assume that nothing happens. Nothing is stated to happen if you land on Free Parking in Monopoly, and thus nothing happens.
So I assumed the same would happen with the card. The rules state "a player's mission order may not be checked by more than one player," it doesn't go on to say anything else. I thought that this would be a reasonable invocation of the "if nothing is stated to happen, then nothing is supposed to happen" rule.
If Tamius did immediately respond to me with that, I would probably not join his games from then on given it's very difficult to play a game and enjoy it when important rules like that are either glaringly omitted or deliberately obfuscated, though I'm willing to give Tamius more of a chance given he was clearly confused by the situation and that it's not something that happens very often.
There's nothing really much of note in the PMs. It was just that I thought the situation was pretty clear-cut while Tamius didn't.
It went like this:
I ordered a KACIOU on Jackson and said I would sabotage the mission.
After the mission was over, Tamius tells me that Jeray used his card, so mine bounced back. He admits not knowing what should've happened here.
I claimed to use the KACIOU, which led to a rules discussion regarding the situation where I though Tamius might have revealed more information that he should have.
Two days later, after the discussion, Tamius then rules I get another chance to use my card.
I ask him if I can't target Jackson.
He tells me that I cannot.
I ask if he'd reveal that I had this possibility.
He told me that he inadvertently already had in the midst of the discussion.
I ordered to scan Falc, and lamented that my game was basically over at this point.