It seems to me that my digital camera will flash a message on the screen if I try to take pictures without the memory card installed. Won't let me take a photo without it. Not sure if they all do that or not. Altho, mine would be very difficult if almost impossible to "fall out". There are two "doors" I have to open up to get to it. My other camera, the batteries would fall out before the card would. Guess it all depends on the camera too.
Hope it turns up somewhere. Luckily, the new ones don't cost nearly as much as they used to! With my first digital camera, between the battery and the card, they about bankrupted me! The real value (and loss) tho is in the photos on the card.