I just flew via Air Canada from USA to Toronto directly. Before boarding, I asked at the gate if any upgraded seats are available. In response, the representative simply gave me a business class seat without any further information. There were a couple more business seats available during the flight, and it seemed like the flight wasn't completely full.
It dawned on me later on that this upgrade may have not been free. The booking was done through an agency my company uses, using the company credit card. I'm worried that the upgrade was not free and was charged to the company credit card. I don't have a frequent flyer status with Air Canada nor its affiliates, nor any other usual reasons for free upgrades.
How can I find out whether this was a free upgrade or not, beside (hopefully needlessly) worrying HR?