VIC Executor of Will Sold Deceased Uncle's Car - No Records?

My uncle recently passed away and had appointed the trust company (professional executors) to take care of his estate. As we had to move him from Sydney to Melbourne to care for him there was a car and furniture that the executor said they would sell on his behalf. We had also offered to go up and get furniture he wanted for him and were interested in buying the car if any counter offers were what we deemed unacceptable.

They got a decent offer for the car of around $6000 but it did not appear on the statement and now the trust company is saying it has all gone too far to find out what happened to it. I understand the furniture would not be worth much at all but how can I make them accountable for the car sale and chase them for the $6000 they owe my family without it costing a "research fee" to find out what has happened to my uncle's car.