It wasn't an accidental delivery charge. I have the receipt. The credit card was run AND THEN I got the receipt. The $3 charge was added AFTER the transaction was finalized. The only way it could have been accidental is if the $3 was a tip on another order and they accidentally added it to my order.
I've worked in all sorts of restaurants from pizza places, to casual fast dining, to black tie fine dining, and I know what happened here. I've seen people do this for years. Most people aren't going to notice a couple extra bucks added to their bill... and if they do notice they're probably not going to say anything... I promise you that if this wasn't accidental (which I'm 80% sure it wasn't) then whoever did it, is doing it to LOTS of other people.
It might only be $3 to me, but I guarantee you that the person running the scam is making a lot more than $3.
I knew a guy that would charge every customer for a soft drink no matter what, but never ring up the drink. He'd pocket over a $100 a day easy. If anyone caught him, he'd just say "Oh I'm sorry I must've charged you for a drink by accident"