There is a difference between the Bank of Canada sending out older series bricks after the launch of a new series and the release of older notes by companies that already have these notes in their vaults. Not every brick that gets sent out to the public is opened and put into circulation right away. I know for a fact that not every business handling large sums of money is going to be ready on the launch date of the new series. Some businesses take months to adapt their machines to new series of notes. If the Bank of Canada tells businesses they have to return all older series notes in exchange for new bricks of new notes, then that pretty much ensures that any notes that have not hit circulation are never going to hit circulation. But if the BoC does not set an immediate hard deadline, there is still plenty of time for Journey bricks to reach the light of day in the coming months. How many of those bricks will be 2011 and 2012 $5 notes (and theoretical $10 notes) is anyone's guess.
The chance of 2012-dated $10 notes existing seems so unlikely given that it would be extremely coincidental that nobody has found one and reported it. The Macklem-Carney $5 notes got out in small numbers as early as 2011, and that's because they were intended to circulate. I just can't imagine the BoC ordering a quantity of notes in 2012 and then putting these aside with no intentions of using them. There would have to be quite a shortage of these smaller denominations combined with delays to the launch of the polymer series.
With the Journey series coming to an end, and with it the practice of putting the printing date on notes, could it be possible that the printers are stale dating Journey notes printed in 2012? Maybe they have the blessing of the BoC to use up old supplies of paper sheets without going through the trouble of changing the printing plates to incorporate the actual year of printing. Altering plates costs money.
