You're very misinformed. Tellers are not running through every serial number from the money they're taking in, that would actually be impossible. There is virtually no way even input a serial number using most Teller systems. Banks have insurance on their money, its an easy insurance claim, thats about all there is to this process. There is nothing illegal for asking for sequential bills, or nonsequential for that matter. You can even directly buy large sums of cash from the fed that gas just been printed. Like even most caught counterfeits bills don't result in anything except the business that took it in losing the value of the counterfeit from their deposit.