It is doubtful there is anyway in which to get your car back from the insurance company at this point. If want to continue to try you can keep going up the chain of supervisors at your insurance company but it is unlikely the answer is going to change.

When you claim was paid out for your stolen vehicle the insurance company gave you a certain amount of money. Now that the vehicle has been recovered the insurance company is selling it at auction to try and recoup some of that settlement money that they paid out.

Though the car might look like it only has physical damage, looks can be deceiving. Thieves are usually not gentle with the car that they have stolen. There might be major mechanical problems under the hood. So if you can talk your insurance company into allowing you to buy the car back, make sure to get it checked out by a mechanic first.