Because of the way mice are kept in research facilities, they are unlikely to escape. This was a clandestine lab, but still probably used the same kind of cages. Even if a mouse did escape, I doubt there would be much of an impact.
Mice are engineered to be infected with human Covid by replacing the mouse ACE-2 receptor gene with the human ACE-2 receptor gene. They are sold to researchers by biosupply companies.
The primary consequence of such mice escaping would be that they might interbreed with wild mice, resulting in a small number of wild mice that have a human ACE-2 receptor gene. I doubt that the human form of the gene would persist for very many generations.
You sound as though you have personal knowledge, so I thank you for the education.