Earlier in the thread this was almost figured out.
My wife left some coins on top of the closed drink holder. I didn't notice them and opened the drink holder, and the coins disappeared. I figured Mazda was crazy for such a design that ate coins, until I looked into the drink holder and noticed that the coins slid out the slot at the bottom of the drink holder.
So the slot is designed to let coins, or other small objects, slide behind the compartment where the lid is kept when opening the drink holder, and exit the bottom.
Judging from some peoples experience, there are some object that can still fit into this area, and now out the slot, I guess those objects will still get stuck.