I bought the extended warranty (or whatever you call it), too. Sure, maybe in retrospect it was not a great move, but coming from a BMW, it seemed like such a bargain (5 years of warranty-whatever for about what a 600 mile BMW service costs -- Suzuki rocks!).
As for extended warranties always being in favor of the dealer, I can say that having one paid huge dividends for my old Jeep Grand Cherokee (great vehicle when it ran right, but what an expensive piece of junk to fix -- I'd never own another Jeep without one), and having one has certainly paid off for my Audi (my, ummm, last Audi ever).
As for the original question, I didn't get a card or packet either. The dealer told me any dealer can look up the VIN. I'd have preferred a card for my $, but I guess you have to trust the dealer.