Normally on Train Sim World, if you derail or collide with another train the simulation stops. Apparently I broke this.
Here is how it happened: I was traveling at about 60mph along the track. Four locomotives in front, a lot of coal cars, and two pusher locomotives in back. On 3rd person view I was able to orbit the first locomotive. When I clipped between the cars, I was able to decouple the first and second locomotive.
Instantly the following train stopped. I kept moving in the primary locomotive. I applied the brake and stopped. I wanted to get out and go survey the situation. However, I forgot to keep the brake applied and slowly the locomotive started rolling backward. Also, for whatever reason, I decided to remove the gas cap. Just for giggles.
After running a while the stopped train despawned. This was odd, so I went back to my primary locomotive. It was right behind me because it was moving downhill. I was still able to jump on and soon it managed to hit the not despawned cars, but invisible. Once it made contact, it was visible again. Cars were tossed to the side, separated from their axles. The video picks up where I run back up the track to survey the damage.