Do you still have the receipt from the trip you canceled in your email? PNR will be on there, and you could do a search using the find command of your browser when your in the canceled flights page.

As for me, I actually just canceled something today, but for some reason, it’s the last record in the canceled section, not the first, as I was expecting. Seems it’s sorted in reverse (by creation date). Not sure if that’s SOP, but maybe that can help guide you.