That's how I learned, too. I wasn't thinking, got to domestic baggage claim and looked for Toronto on the board. When I asked, a SkyCap, who I've used several times when I have boxes, shook his head and said, "Canada isn't domestic." I had flown into Erie, so I collected my car on that side of the airport, drove over to the International side, parked and paid again - it took for that fifteen minutes - and went into the International Terminal to get my bag. On the International side, not the Domestic side. Because Canada is International. Which I now know. I posted a warning to others at the time, thinking I was not the only one who wouldn't think of Canada as International.

BTW, I wasn't even the only person on my flight who went to Domestic, but we were told by others on the flight, when we got to International, that an announcement had been made onboard. I gotta start paying attention.