Game of Chance - Now you see it, now you don't

We went through a tough time. We used our wedding rings and my engagement ring to generate some cash (Last gasp type thing). I was late coming to collect but paid up with interest. I got my husband's ring but they said they couldn't find mine and would I come back tomorrow? This was a Friday -went back on Saturday they still could not find it. Went back for the third time - still nothing. I wanted a refund and they tried to underpay me. They had the goods, and their computer says the ring is in the safe - only it is not. This is a huge breach of trust. Their system says it is there but they can't find it - how many other things go missing? The attitude of staff was also disinterested and not at all helpful. At some point, something went wrong and the only conclusion can be that it was ****** out of the safe. Find it or pay up.