Well, it was discovered that some sharp rock shards that were proclaimed to be early human-made hand tools turned out to be from rocks broken by monkeys who are after the salty cores and have no use for sharpened bits of stone themselves. (Though there are other monkeys who do apparently use stone as tools, not to mention the ape populations that habitually use non-stone tools.)

Humans like to see themselves in everything. Yet I doubt they would recognize a truly non-human civilization unless it could nuke them in their silly ape faces.