Had this happen to me last week where I stood by for an earlier rapidair YOW-YYZ and got on, ticket was mistakenly changed from Tango + to Tango. Called the AP number on the back of my card, they said to call Air Canada. Wrote an email to AC and they responded in 2-3 days with the same answer, "take it up with Aeroplan." When I told them I'd been passed to them by AP, they promptly took care of me and credited me the appropriate miles. I think it helps if you can provide them with both the ticket # and the PNR, as well hopefully you saved your BP.