i placed the melted chocolate in the fridge after using the chocolate fountain?!

well you gotta remember that oil is a very light liquid so yes it will raise. the chocolate should harden from the heated chocolate. when it is heated and all bendy and gooey it will then harden when its coolen. its like making a sword. you heat it up in the fire. pound it and put it in an ice cold water. did you happen to put the chocolate right in the fridge when you were done at the min? or did you wait some time? that can be the reason. now the science to it is because as chocolate heats. the particles in the chocolate tend to move vigorously. when the chocolate is cold the particles will slow down making the chocolate harden. this goes with all substances and matter. its basic laws of matter that make up this schocking piece of evidence :P

because a mouse is in it.