There really isn't any proof. We get takeout 1-2 times a week, sometimes cold. It has never crossed my mind to worry about reheating anything.
https://www.npr.org/sections/health-shots/2020/04/08/822903487/how-safe-is-it-to-eat-take-out
The coronavirus that causes COVID-19 is primarily spread via droplets expelled through coughing or sneezing, says William Schaffner. If you're standing too close (within about 6 feet) to an infected person when the person coughs or sneezes, or
even possibly when the person speaks or exhales, viral droplets could make their way to your nasal passages and mucous membranes. Or if you touch a surface with droplets on it and then touch your eyes, nose or mouth, that could also lead to infection.
All this means that transmission via food is incredibly unlikely, say both professors Schaffner — unless you actually inhaled your food. "Even in the so unlikely scenario of virus through a sneeze or cough coming into contact with, say, a salad, that would enter the body through the throat," William Schaffner says.