There are AC coolant lines running to the back of the vehicle on the left side. This is the AC system for the hybrid battery. I would assume as the temperature started rising the battery was not getting cool enough to allow EV mode. I've seen other posts on this site about various issues with service. Seems that we know more about our vehicles than some of the service techs.

I'd keep a close eye on your car to make sure no permanent damage was caused to the hybrid battery as a result of not having refrigerant in your AC. The battery warranty should be long enough to cover any long term issues. Not sure what your warranty is in Canada. Here in California the warranty is longer than other parts of the US, 10 years/150,000 miles.

Good luck.