Eventually we're going to find our old stuff somewhere in the solar system, but we'll have forgotten that we left it out there, so we might one day think it's alien stuff.
https://prizeo.com/r/kyCA9n Donate and try to win a seat to space, now that would be cool... we can dream
This is about a month old, so some have probably already read about or heard about Avi Loeb's new book called Extraterrestrial: The First Sign of Intelligent Life Beyond Earth. This New Yorker article discussing the book is a well-written review that discusses the plausibility and implausibility of the object found in 2017 being extraterrestrial. (I think I might buy that book.) "Have We Already Been Visited by Aliens?" by Elizabeth Kolbert https://en.wikipedia.org/wiki/ʻOumuamua