I think it may go straight into your "banked" money. Or I had the same thing happen and just thought my balance had gone up, but didn't pay close enough attention to know. Otherwise, that really stinks.
I don't play nearly as much as you guys. I also had a 6 month forced absence when I had no internet, which I think is the biggest factor. My character is only level 131! I spend all my money slowly upgrading my cars, so I'm always cash poor. Remember the Compact Cup when I had to rob a store to get the entry fee, lol. That happens to me a lot.
I also stopped banking my money for the most part. It seemed silly to bank it if I was just going to spend it right away.