Suppose no member of a certain kind of animal survives. If the nature described could apply to distinct individuals, the absence of current instances does not destroy its universality.
Conversely, “this precisely identified person who stood before me yesterday” remains particular by its referent, whether that person is now alive or dead.
Keep two questions distinct:
1. Can the meaning itself apply to many? This decides universal versus particular.
2. Are any instances of that meaning actually present? This concerns their existence.