Imagine the following situation:

I am at home. I put a small diamond inside a glass cup. I put the cup on tray, and then carry the tray to the kitchen. In the kitchen, I put another cup on the tray. I then carry the tray with the two cups on it to the bathroom. I pick up both cups and turn them completely upside down over the counter next to the sink, so that there is nothing preventing what is inside of the cups from potentially falling out. I then put the cups back on the tray and carry the tray to the living room.

At the end of all this, where is the diamond?