I don't think there is any way we'll find out. If it escaped the lab, the lab people might not even know, and if they did know, it would be covered up just as tight as possible by the person who erred, and if not successfully covered up, it would be covered up by the CCP.
Our WWII hx lesson in a 1960s elementary school regarding Hitler was that while there was evidence he committed suicide uncertainty remained as to whether he escaped. We didn't know with certainty until after the Soviet Union disintegrated.
If the virus escaped the lab, and if the Chinese government actually knows it, maybe we will learn someday, should the Chinese government fall. Strange things happen with governments. I am not looking for the CCP and its government to fall in the foreseeable future.