I can answer this dannyj.
1. It's against the rules.
2. But if it happens they cannot deny you the jackpot.
3. For all practical purposes no one will care.
4. Could some asshole take action against you and delete points from your account? Yes. But is it likely to happen? No.
There's time between hitting the jackpot and when someone shows up... so switch the cards. The slot attendant won't know.
If you get caught just say, oops wrong card. They won't shoot you.