I wondered the same but I would expect a business of that nature and size to have good CCTV and monitored security, they are responsible for a lot of peoples cars, and also have expensive paint, tools, computers etc on site that would be regular burglary targets.
And so IMO police would have checked that CCTV footage and would know if a customers vehicle or a company vehicle had been taken on say Saturday afternoon, and returned Sunday morning. There would also be other businesses in the area with CCTV, so a good chance of more footage of the vehicle heading out and coming back in to the street? I think if this happened it’s an easy one for police, there would be enough to go on to arrest someone fairly quickly while investigations continue, while they question the accused. So they would have moved in long ago.
There is always the possibility that someone experienced at crash repairs has undertaken the repairs elsewhere, eg in a back yard garage, so the car may no longer look damaged. That could be a disgruntled employee, or competitor. I worked briefly in a panel beaters and there were a lot of dodgy characters in the trade, it could be a legitimate business run by SM and MM that was infiltrated by bad actors, or under pressure / standover tactics from dodgy competitors.