Go into that dealer with a "give me my cards or give me my money back NOW" mindset, and take NO excuses whatsoever.
I just wish I had been educated enought to know about this when an AD ran what I now beleive to be a gray market used 2296.80 in on me with just the warranty card instead of all three, and the watch flat out BROKE three weeks after I got it. (One of the plubger seals was stipped and pulled out.) Three months later I had nothing to show for being the owner of a 2296.80, the watch never came back, and I finally got my money back. My ignorance on the matter of how many cards there WERE supposed to be prevented me from understanding how badly I had been taken advantage of, and if I had known then what I do now, that AD would have had a 6'3" 250 lb. customer cursing her out at the top of his lungs, and letting everybody in the place know that they were dealing with a crook.
Forgetting to put all the cards in the box is not a common mistake, and at the very least it means that dealer is unacepptably sloppy. It could be evidence, however, that the watch is used, gray market, or God Knows what. Good luck, and don't back down!!