Batteries sometimes fail before their time, and there can be numerous other reasons for it going dead. One common problem is corrosion taking place under the terminal clamps. The first thing I do in a case like that is remove the terminals one at a time and see if they're corroded. If so, clean/lube and you sometimes will start up and drive away. If they're clean, either the battery failed, did not get adequate charge or the vehicle has a current drain. Since I have a 2/10 amp charger, I would see if it will charge up enough to start. If so, then I drive to a dealer (with a car under warranty) or an auto parts store for a charging system check. If it won't take a charge, the battery will have to be replaced.
Another fairly common problem is a loose cable or loose/corroded ground connection(s). I imagine they use salt on the roads in NS, and cars there or other such areas require special care for corrosion. Since you had the anti-corrosion treatment done, you already know this.
I'm left with the feeling that they charged it up and you drove home, so all you can do is use it and take note of any symptoms developing such as slow starter RPM, dim lights, etc. There is only one thing for sure; if it did it once, and there was no corrective action, it will do it again, and at the worst possible time.