Ramshorn snail coming out of its shell??

[tropicalfishlover1]

So, I noticed in my 5-gallon shrimp tank that one of my massive ramshorn snails wasn't in its shell which was wedged between a piece of wood and rock. Then as I looked closer, I saw 2 slug like things, which were the colour of the snail's flesh, moving around the tank. What happened??

 

[Waterbabe]

I keep Ramshorn but in no means an expert. So it's a total mystery, the snail shell develops inside the embryo and is attached to the mantle. Living outside of the shell would make its life almost impossible I would of thought. The fact that he was wedged makes me wonder, did he strain to come out and ripped the delicate membrane in desperate attempt to get out. Strange? Do you have pics to show?