The license plate story is useful, but it does not address the uniqueness problem. We see lots of license plates, and there's nothing particularly special about

The license plate story is useful, but it does not address the uniqueness problem. We see lots of license plates, and there's nothing particularly special about most combinations of characters. We see lots of rocks, too, but until Oumuamua they were all solar. The distinction between solar and nonsolar is meaningful; indeed, many astronomers have wanted to see a rock from outside the solar system for a long time.