Let's say you let your friend borrow your car. The gas tank is half full.

He then returns your car with a half full gas tank. Did you lose gas?

Ok.ok.ok.

Let's say you're at an all you can eat buffet. You want one piece of cake when you are finished with your meal.

You notice the cake is dwindling, so you make your way to the display of food. As you near the cake, a small group of people take all the remaining cake.

You are forced to wait until the restaurant staff replenishes the cake. Did you lose cake?