Diamond Fell Out of Ring After two days

On the 17th of July i went to purchase my fiance an engagement ring, i spoke to the consultant and we agreed on a particular ring. I paid the full purchase price and left, on Monday the 20th July my Fiance returned to the store to get something engraved on the ring and whilst she was there the main diamond in the ring fell out. She was truly devastated by this and called me crying and complaining. No body at the store came to console her or even a manager came to tell her what the process is etc. My reputation has been tarnished at her family and with her friends and i am now labelled as being a cheap skate. I chose Browns cause it seems liked it stood out and have great craftsmanship and workmanship. I was disappointed to hear my wife cry and get no assistance from your company. I had to take a day off in order to sort this out and there was no solution. All i was told is that this happens all the time. How can that be an answer when i had only bought the ring 3 days ago. I am thoroughly disgusted and disappointed.