Claim authourised, car's whereabouts aren't known

I had an accident on the 29th July, MIWAY Insurance then sent towing company A1 Assist to collect my car. Repairer at Monument Panel beaters had given me a quotation and MIWAY called to confirm authorisation of body work. Upon checking up with repairer after two weeks, I was told that unknown person took my car and whereabouts aren't known. Both MIWAY and A1 Assist didn't know where it was until I called my Tracker to locate my car and it was found to be at A1 Assist address. MIWAY and Monument Panel beaters were negligent, my car could have easily been in another country. I am sitting here with no car hire for 19 days. This was very POOR SERVICE, I am disappointed.....