I can't remember what show it was (maybe Futurama?), but there's a great bit that lampoons this idea. At a modern art exhibit, somebody leaves something like a banana on an empty pedestal. Later, the attendees are marveling at it, talking about what it means, that sort of thing.

In that is example, there is no artistic intent, but also, the "piece" cannot be readily separated from the other "pieces" in the modern art exhibit that were made with artistic intent.

By your definition of art, people can be "duped" by facts about a piece that don't even accompany many pieces that we think of as "obviously art". They can assume they know the answer, or even a bounding box for the answer like "it was made by a person intentionally", and they can turn out to be wrong, and then... what? It just wasn't art, retroactively?

What if a famous haiku turns out to have been a coded message, 100% instrumental in nature, something like the number and position of enemy forces? "Whoops, guess it wasn't art". What if the best picture I took on a vacation turns out to have been take by a software glitch while my camera sat on my luggage?

We only ever think we know who made something. We do get it wrong. There's a lot of fraud in the art world. Is that likely to get worse or better in the next 100 years, do you think? What are future generations to do, just wonder about whether all their favorite art (that looks like art, feels like art, moves them like art) is "maybe art, maybe not"?