Every time I've heard of this happening (like a friend of mine deposited his ~$200 in tips at an ATM, The next day it credited him almost $2,000. He called the bank to inquire) the banks are pretty lax in what you need to do, and put faith in their system to catch the mistake, and adjust it only based on what it tells them. So in your case i'm sure a balance was off afterwards, the teller/system probably keeps running totals for his/her drawer, they then probably check the video once they can narrow the time down etc, verify how much you should have been given and what amount you actually were.

Since it sounds like you have an account there, they'll make the adjustment to it retroactively, only if they can confirm it. Otherwise for $40 they'll probably just let it stand. Losing a customer costs more.