I've been 50k for all of 2014 (first year), never once showed my card the whole time. It always is on my boarding pass and I took that to be good enough. I keep a picture of my card on my phone (wallet diet) and I know my aeroplan number. At least 1 of those 3 things gets me in every time.
That said, I don't travel TOO much internationally...however PTY,BOG,MDE,DEN,SFO,IAH,ORD,SAL all let me in without a card as well. I get the most flack at YYC but they always end up letting me in after a 30 second conversation.
Sidebar: do you guys show your card to non-MLL international *G lounges? Are they even linked together or do they just wanna see that you have the card?