Lost Identity Document

At the end of April 2017 my husband and I used Uber for transport to the South of Johannesburg. The Uber experience was wonderful and very efficient. However, my Identity document was left in the Uber car on our trip back home. We contacted the driver of the Uber and he confirmed that he had my Identity document and we would arrange to meet to collect it. The problem came in, when this particular Driver was not actually the Owner of the Uber car and within the next week or so, the Owner of the car and himself had some or other altication, and now the Owner of the car has my Identity document and will not answer his cellphone. This is 7 months down the line and I want my Identity Document back. When you respond, I will offer all the details of this particular Driver. Please assist. Thank you