> the police somehow got said evidence after the person left, and they know the person's identity Yes. The police often show up after a crime has been committe

> the police somehow got said evidence after the person left, and they know the person's identity Yes. The police often show up after a crime has been committed and the suspect is long gone. If their investigation turns up clear evidence (a witness who knows the person, surveillance footage, etc) then they might be able to issue a warrant for that person.