they can get resourceful that's for sure. A family friend had a catalytic converter stolen in the parking lot of a grocery store when they stopped to pick up a few things. Stealing a catalytic converter involves cutting parts of the exhaust system out of a car.
It takes about 30 seconds to make two cuts through exhaust pipe with a one handed battery sawzall or battery angle grinder.
https://www.homedepot.com/p/Milwaukee-M18-FUEL-18V-Lithium-I...
Skilled thieves can do that with a battery powered saw in less than 30 seconds, there's been more than enough videos on youtube showing just how easy it is.
Cheap battery powered tools have made a lot of crime a hell of a lot easier.
Just wait for the drones that bring the saw and haul away the converter.
A lot of Priuses in my neighborhood lost their catalytic converters a few winters ago. Mostly this happened at night, so there was more time than for whoever hit your friend's car..
so in defense, you can have a catalytic converter cage put in, but it seems they will just cut through that as well to get at the catalytic converter.