Good suggestions above, but Jack, why is it so onerous to just pop into the concierge office? If you're just connecting at YYZ, okay, but if YYZ is O/D, you have to walk past that area at some point anyway.

Knowing the organisation of concierges vs MLL agents, I expect that if you went to the concierge office, you would have the package within seconds, because they're used to dealing with stuff like that, whereas the MLL crew might take a couple minutes to find it.