OP: I think the restaurant treated you horribly regardless of your history with them. What they said isn't the issue. I'm sure the people you talked to were simply stating restaurant policy regarding this particular situation. They have to apply the same policy to everyone who can't pay regardless of why they can't pay. The issue is HOW they expressed themselves. And it was simply horrible. Rude, humiliating, and incredibly bad customer service, and bad customer service means bad publicity which means fewer customers. The diners who witnessed this may have believed you made an honest mistake and were shocked at how you were treated. After all, it could happen to them. Congrats on sticking to your guns!

In case you didn't know, when debits and credits hit your bank account, the bank will process the debits before the credits. This is how people wind up with overdrawn accounts due to making purchases while the account balance is so low - even if the bank statement says you have enough money to cover the purchase. Nasty, huh?