I agree with Stinger and the others, this is what AC needs as it will not be reinbursed without the ticket segment coupon.

But I am a bit confused by your post:

"On my flight back to YYZ from VIE, I was on the same flight with a group of students coming home from a study trip. The flight made a stop at LHR before proceeding to YYZ. I was sitting close to the entrance of the gate and overheard what was happening."

What I read from this is that you were flying on AC metal from VIE to YYZ. However, AC does not fly between VIE and YYZ, OS does. And OS does not make a stop at LHR en route to YYZ. So perhaps you can clarify this for us, or at least for me?