A Walmart in Mississauga just sent 1,453.60 to my credit card, What do I do?

Like they sent ME the money, not charged me. What are the rules here? Do I need to report this right away? I know not to use the money obviously but should I just let it sit as if I have no idea about its presence? Is there a time limit before I can claim the money as mine?

Thanks for any input.