Solicitor missing with money!!

Hi
My father died 1 yr ago and he left a substantial sum for my mother. At the time we were selling the house and therefore we wanted to leave this money until the house was sold and when she found a new property. The bank and estate agent gave us the name of a solicitor and he told us that he would hold the money for 6 months until a property is found (he said is was common law). We transferred him the money and he stamped and signed a document of which we have a copy saying he received it. It was a document saying that he received the money and that if my mother died, the money would be transferred to us or if she found a property the money would be transferred for the purchase.
But....in the last couple of months, the solicitors website, phone numbers and email address have stopped working. The guy he was a partner with has transferred to a new company. Would the partner be liable? This money is now missing as we can't get hold of the solicitor.
Any advice would help