Using my debit card has always resulted in an immediate debit from my account, as far as I know. Kinda thought that was the point (though, the Canadian debit system operates differently than the American system). It's possible they didn't debit your account until the item shipped. It's also possible the long weekend has delayed the debit going through. I would make sure you have enough money in the account to cover the transaction until you see it go through. After a few days, you might want to check to see what's going on.