The toughness claims seem a bit overstated in some contexts, e.g. the paper linked in the post compares it to the average toughness but doesn't compare to other outliers not suspected of being artificial, while the Wikipedia article for CNEOS 2014-01-08 compares to other outliers but uses the the high end of the strength estimate.

I think trying to retrieve it is a good idea, but I also get a whiff of motivated reasoning in most articles describing how unique it is.

All of the heavier metals on earth came from outside of the solar system (such as, for instance, Tungsten). How much of the ore deposits on earth do we attribute to extraterrestrial technology? I'd wager none.

All our own technological signatures will be reduced to odd mineral deposits if we wait long enough. On a planet with active geology like Earth, tens of millions of years should be quite enough to do it.