I have looked in to this matter and forwarded your complaint to several departments to get a better understanding on how to handle this situation. As you can imagine this is a unique situation, retailers don't experience this quite often. Scotia Bank was also contacted, and what they explained is, in this case they would want the customer to call the 1.800.472.6842 (located on the ATM machine) or present the torn bill and the receipt to the bank and the customer would be reimburse. Or if you are not a Scotia bank customer you could bring it to any bank and they would also reimburse you.
Customer Service Representative
Shell Canada Limited
PS - I still haven't heard from Scotia Bank.
PPS - Don't let businesses (B2B or B2C) treat you like shit and get away with it.