Jewelry Exchange Didn't return the ring that I gave them Villa Park, Illinois

I purchased a diamond from here back in March, I had it set in my mothers setting, I was not happy with how it was set.  It was too low.  I dropped it off and left it to have a new head put on it.  When I picked it up it didn't look quite right to me, it is a tiffany setting.  But there wasn't much I could do. 

I was just looking through pictures and found a picture of the original ring and I was right the ring was switched, due to the fact that the sentimental value of this item is priceless and I am extremely upset with the fact that my Mothers ring is gone.

This happened in March of 2010, I have been going back and forth with them and their response is for me to go and spend more money on a setting I like.  I really want to start a class action lawsuit against them and would like anyone interested in being involved to contact me.