Originally Posted by
pewpew
Under IATA agreements, the final airline on a single reservation takes responsibility for the bags, so...
+1 - It doesn't matter. Whoever screwed up and lost or misplaced the bag, it is the final delivering carrier which must arrange for delivery and make compensation to the passenger. That carrier can then settle up with the "screwing" up carrier, but this does not involve the passenger.
The greatest mistake is to pursue two different carriers at the same time. Confusing messages in the system and routinely, the bags take longer. In this case, the carrier handling YYZ-MCO would be responsible.