Wow, this is certainly a wakeup call that I need to brush up on the security features for paper bills.
Guess I’ll have to chalk the loss up to a 100$ learning experience.
Try not to be too hard on yourself. I could tell you of some of my very expensive "wake-up calls" when I first started to collect paper money. Learning how to properly grade a note is probably every collector's harshest "learning curve." I believe this is essentially as a result of our lack of exposure to excellent uncirculated notes and one's deep wish that the note in possession (or about to be purchased) is in fact in better shape than it actually is (we all love a "deal").
Some of us here still actually trust the 3rd party grader (& the assigned grade on the note holder) rather than taking the time to inspect the note in as thoroughly critical light as possible. The situation is changing: since many dealers (or collectors operating as "dealers") have had their rarer stock sitting online marked up much higher than book value in US dollars (graded by a popular US grader) and have been waiting (months to a year) for new collectors to hit the "Buy it Now" option. I believe collectors are getting wise because of sites like this one and because all you have to do is go through a "Wake up call" of buying a note at what you believe is a much higher grade- then take it to "show & tell" amongst other veteran collectors who could easily dispute the assigned grade (changing the value of the note considerably). Its a hard lesson to swallow.
If I were to start collecting coins I would probably go through many similar hard lessons in my purchases since I'm not well versed in coin collecting (esp if I were to buy "raw" notes with little info at my fingertips).
The best way to protect yourself from that (if you are still interested in collecting Cdn paper money) is:
a) avoid "error" notes & especially notes in higher denominations (fewer collectors are interested in higher denominations of the more recent series anyways)
b) educate yourself by examining regular older (Journey or Bird) notes you can get at face value to see for yourself what the security features are
c) take a look at the Charlton Standard Catalogue "Canadian Government Paper Money" which most libraries carry. If you cannot find a copy at your local library than you could buy a cheaper (older) edition online or the 2017 29th edition at Chapters/Indigo (& online). The catalogue is a wealth of info that can help guide you in terms of what to collect as well.