The shell

Once I was walking on the beach, just wandering around, enjoying the sun and the warmnes... then I found something that seemed like a shell or a piece of rock. At first, I just had stepped on it and that is why it caught my attention. When I crouched to take a better look at it, I saw a small shell. It was full of sand, covering all over it. It seemed normal.
I just put it apart and went on. But something about that shell stayed in my mind. I thought I had seen some color, some shine on the shell, but all the sand was blocking me from seeing it.
Then I came back again and looked for the shell. I was so happy to find it again! The sea hadn't taken it. Then I dusted the shell a little bit and saw how beautiful it was. It had a beautiful mixture of colors and shined on the sun.
I decided to wash it in the sea to better see its shine and colors. I totally fell in love with that beautiful colorful shell, so shyly hidden in the middle of the sand!
But then, when I was washing it in the sea, I was careless and, before I realize it, the wave took it away from me! It was such a stupid wave and I don't know how it happened! The shell was with me and, all of a sudden, it was gone! I couldn't take good care of that beautiful shell in the few minutes I was with it... and it just slipped through my fingers into the sea.

I entered the cold sea to look for it, in the hope to see it and get it again. But it just vanished in the middle of that cold water. And I still don't know what exactly I did wrong that made me lose my little beautiful shell.