First, they set rules and if you break them, you just cannot blame them for making you abide by them. There are several ways around this as pointed out in another thread. Tell them it's $4k of camera gear (if they call you out on it) you'll need to them ensure that they'll replace for the full amount.
Otherwise, if you have NOT already walked up to the counter, leave the bag behind with someone else and make sure they don't see it. Don't tell them you have the bag. Then retrieve your bag and go through security. Done.
To be honest, this is NOT Air Canada's fault. ANY airline and ANY ticket agent can call you out on this. First, you broke the rules. Then you just got a bitch/unlucky.
You have a couple of photos that are great... you must be very good at photoshop!